CoCounsel vs. CASUS: US platform vs. Swiss legal AI

CASUS is a Swiss legal AI platform built for law firms and in-house legal teams, covering contract work directly in Microsoft Word or via a web app. It is hosted in Switzerland and the EU, transfers no data to the US, and offers Zero Data Retention with no human review of your documents. CoCounsel by Thomson Reuters is a capable tool for US-based legal practitioners - but for Swiss teams with FADP and GDPR requirements, the comparison matters. This article explains where the differences lie and why they become concretely relevant in day-to-day mandate work.

What is CoCounsel?

CoCounsel is Thomson Reuters' legal AI platform, integrated into the group in 2023 through the acquisition of Casetext for approximately USD 650 million. The platform relies heavily on the Westlaw database - one of the largest US legal research infrastructures - and is aimed primarily at US attorneys and large law firms in the English-speaking market.

The core offering covers AI-assisted document review, legal research, contract drafting, and Q&A via a chat interface. CoCounsel is deeply embedded in the Thomson Reuters ecosystem, which creates friction for teams outside that ecosystem - particularly when neither a Westlaw licence nor English-language contract work is central to the practice.

Why do Swiss law firms look for a CoCounsel alternative?

Data residency, Art. 16-17 revFADP, and the US hosting problem

The most significant concern for Swiss users is legal in nature. CoCounsel stores and processes data on US infrastructure. For law firms that process mandate-related contract data, this is concretely problematic under the revised Swiss Federal Act on Data Protection (revFADP / revDSG, in force since 1 September 2023).

Art. 16 revFADP permits the disclosure of personal data abroad only where the recipient country provides an adequate level of protection or where specific safeguards exist - such as standard data protection clauses or binding corporate rules. Art. 17 revFADP sets out the permissible exceptions exhaustively: consent of the data subject, overriding private interests, or a legal basis. The Swiss Federal Data Protection and Information Commissioner (FDPIC) does not treat the United States as a country with an adequate protection level in general terms. A firm that processes mandate-related data - party names, contract content, due diligence materials - on US servers must therefore be able to demonstrate one of the Art. 17 exceptions. In daily practice, that is rarely straightforward.

The GDPR dimension compounds this. Swiss firms acting for European clients, or processing data of EU-based individuals on the counterparty side, must also comply with Art. 46 GDPR, which requires appropriate safeguards for transfers to third countries. Art. 28 GDPR additionally requires that processors - and a US-based AI provider is precisely that - be engaged only under a compliant data processing agreement, with technical and organizational measures documented in accordance with Art. 32 GDPR.

In its 2024 guidance on AI systems, the FDPIC clarified that companies using AI services as processors must extend data protection requirements fully to the AI solution, including transparency about sub-processors and storage locations. A "Zero Data Retention" commitment alone is not sufficient when the processing infrastructure sits in the US and no adequacy decision by the FDPIC exists.

CASUS hosts exclusively in Switzerland and the EU, transfers no data to the US, and provides both Zero Data Retention and no human review of uploaded content. More detail on the infrastructure is available on the CASUS security page.

Westlaw dependency and Swiss case law

CoCounsel is tightly aligned with Westlaw. Teams that need to research Swiss case law, cantonal court decisions, or Federal Supreme Court rulings get little from that setup. This is not a marginal problem. A Zurich M&A partner assessing a warranty exclusion clause in a share purchase agreement under Art. 197 et seq. of the Swiss Code of Obligations (CO), who wants to reference BGE 144 III 327 - the Federal Supreme Court's leading decision on liability disclaimers where defects were fraudulently concealed - simply cannot do that through Westlaw.

CASUS searches over 660,000 cantonal and federal decisions and displays the relevant legal reasoning sections directly in the answer, with no click-through to an external system required. See the legal research page for more.

Pricing and ecosystem lock-in

CoCounsel is structured as an enterprise subscription typically tied to existing Westlaw contracts. For smaller firms or teams without a Westlaw subscription, the additional cost is substantial. Pricing is not public - Thomson Reuters communicates it only through direct sales conversations. CASUS requires no Westlaw licence; the platform can be tested directly at app.getcasus.com/signup.

The EU AI Act regime from 2025 and its relevance for legal AI tools

Since the EU AI Act began entering into force in stages from August 2024, with most provisions fully applicable from August 2026, AI systems used in legal contexts that can affect the rights of natural persons are potentially classified as high-risk - particularly where they are used in proceedings with legal effect (Annex III, EU AI Act). While the regulation primarily addresses EU providers and EU users, it affects Swiss firms working for EU clients or operating cross-border. Providers that transfer data to the US must demonstrate compliance not only with data protection law but also with AI-specific transparency and documentation requirements. Tools hosted in Switzerland or the EU face structurally fewer evidentiary problems here.

Liability risk analysis: what happens when mandate data lands on US infrastructure

This section is missing from most CoCounsel comparison articles - and that gap matters. The compliance question is not abstract; it has concrete liability consequences.

Consider a realistic scenario: a Zurich boutique firm with eight lawyers is working on a share purchase agreement involving a German buyer and a Swiss target company. The SPA contains personal data relating to key individuals - management warranty representations, board members, beneficiaries. The team uploads the document to a US-based legal AI tool to run a risk review.

What concretely follows:

First, the transfer of contract data to the US constitutes a cross-border disclosure of personal data within the meaning of Art. 16 revFADP. Without prior verification that one of the conditions in Art. 16-17 revFADP is met, the firm may be acting unlawfully. The FDPIC can open investigations under Art. 49 et seq. revFADP.

Second, Art. 28 GDPR applies separately towards the German buyer. If a US sub-processor handles the data without a compliant data processing agreement, the firm is exposed vis-a-vis its client - particularly if the buyer later raises a data protection incident.

Third, Art. 398 CO (the duty of care owed by a mandatary) requires a lawyer to act with the care of a prudent professional in the client's interest. Processing mandate-related data in a third-country tool without reviewing data residency risks a breach of that duty, with civil consequences under Art. 97 CO.

For the Zurich firm: at average hourly rates of CHF 400-600 for senior associates and CHF 600-900 for partners, the compliance cost of retrospective documentation and potential notification obligations under Art. 24 revFADP can quickly exceed the time saved by the AI tool. Firms using Swiss-hosted solutions like CASUS avoid this risk structurally.

What to look for in a legal AI platform

When evaluating an alternative to CoCounsel, these are the relevant questions:

• Where is data hosted and processed? (Switzerland, EU, or the US?)

• Is Zero Data Retention and no human review in place?

• Is the platform built for Swiss law and German-language documents?

• Does it work directly inside Microsoft Word?

• Does legal research cover Swiss courts and cantonal decisions?

• Is pricing transparent and scalable?

• Does the provider meet the FDPIC's 2024 requirements for AI processors?

CASUS as an alternative: what the platform concretely offers

Contract analysis and risk assessment

The Risk & Quality Review identifies risks and weaknesses within individual contracts, assigns them to the relevant contracting party, and prioritizes each finding by severity - low, medium, or high. Each finding comes with concrete drafting suggestions that can be applied directly in Word, correctly formatted, with no copy-paste required.

In practice, Risk & Quality Review findings on SPAs show a recurring pattern: missing or uncapped liability provisions, vague material adverse change definitions, and incomplete IP ownership clauses appear as the most common high-severity flags. These are exactly the points that experienced counterparty counsel targets first in negotiations.

Playbook comparison: the Benchmark workflow in NDA practice

The Benchmark workflow checks a document against a reference standard - for example, an internal playbook or best practices for an NDA, SPA, or DPA. The platform surfaces missing clauses, incomplete provisions, and deviations as structured findings, and includes a percentage score for how closely the document matches the standard.

Anyone who reviews NDAs regularly will recognize this problem: Swiss and German template NDAs often diverge significantly in how they define "Confidential Information." German templates frequently include oral disclosures automatically, provided they are confirmed in writing within 30 days; Swiss versions often omit this confirmation requirement and define the scope more broadly but less precisely. Under Art. 321a CO (employee duty of loyalty) and Art. 162 of the Swiss Criminal Code (breach of trade secrets), the choice of definition has concrete consequences - for instance where employees of both parties are to be bound by the NDA. A second recurring finding: missing or inconsistent governing law clauses. Under Art. 116 of the Private International Law Act (PILA), parties are free to choose the applicable law, but many NDAs in the Swiss market either lack a choice-of-law clause entirely or include one that conflicts with the Swiss contractual statute - a deviation the Benchmark workflow flags automatically, but which often goes unnoticed in time-pressured manual reviews.

AI Chat and Agent Mode

The AI Chat answers questions about a document, links answers to the relevant source passages, and lets users jump directly to the relevant text. In Agent Mode, CASUS executes changes directly in the document - inserting clauses, rewriting text, checking consistency - while respecting structure, numbering, and formatting. The AI Chat product page covers this in detail.

Swiss legal research with 660,000+ decisions

The Legal Research mode draws on over 660,000 decisions from Swiss cantonal and federal courts, as well as statutory law. Results are structured and traceable - not generic internet answers. Relevant reasoning sections appear inline in the response, so there is no need to open a separate research system.

That is not the same as a full legal assessment - but for a structured first evaluation, supporting a clause rationale, or quickly locating a leading Federal Supreme Court decision, it is a concrete speed advantage over manual searches in decision databases.

AI Data Room and Proofread

For due diligence projects, the AI Data Room handles the parallel analysis of dozens to hundreds of documents using user-defined extraction fields. The Proofread module checks contracts for linguistic consistency, Swiss spelling conventions (ss instead of ss), cross-references, definitions, placeholders, and formatting - without altering legal meaning.

Teams that want to try the platform can register directly at app.getcasus.com/signup.

Workflow cost comparison: a ten-lawyer firm, NDA review process

To make the difference tangible, consider a hypothetical but realistic scenario: a Zurich boutique with ten lawyers processes an average of 20 NDAs per month, of which 12 require review as the receiving party.

Without legal AI: An experienced associate at CHF 400 per hour typically needs 1.5 to 2 hours for a thorough NDA review, including commentary and a governing-law check under Art. 116 PILA. At 12 NDAs per month, that is 18-24 hours, or CHF 7,200-9,600 in associate time - before partner review time.

With the CASUS Benchmark workflow: The Benchmark run produces a structured findings report in minutes: which clauses are missing, which deviate, where the governing law clause is inconsistent. The associate starts from a structured baseline rather than from scratch. A realistic time saving: 40-60 minutes per NDA. At 12 NDAs: 8-12 fewer associate hours per month, equivalent to CHF 3,200-4,800. Annualized, that is CHF 38,000-58,000 - before partner time and opportunity costs.

These are not guaranteed figures; actual savings depend on document complexity, firm structure, and workflow integration. But the order of magnitude shows why the licence cost of a Swiss-hosted legal AI platform reaches economic breakeven quickly.

Comparison table: CoCounsel vs. CASUS

Who is CASUS the right fit for?

CASUS fits Swiss law firms and in-house legal teams that have the following concrete requirements.

German-language contract documents in a Swiss legal context. Teams working on SPAs, NDAs, DPAs, and other contracts under Swiss CO need a platform that understands these document types and the underlying case law - not a tool calibrated for US common law.

Data-protection-compliant infrastructure without ongoing compliance overhead. Under Art. 16-17 revFADP and Art. 28 GDPR, the firm must be able to demonstrate that its AI processor meets the requirements. Swiss hosting with Zero Data Retention and no US data transfer eliminates that verification burden.

Direct integration into the Word workflow. Firms that do their contract work in Word do not want an additional media break. The CASUS add-in enables review, benchmark, chat, and proofread directly inside the document.

Swiss case law as a research substrate. Teams that rely on Federal Supreme Court decisions and cantonal rulings need a database that covers them - not Westlaw.

Teams using CoCounsel primarily for US law and the Westlaw integration will continue to be well served there. For Swiss conditions, CASUS is the more targeted solution.

More information is available on the product overview and the about page.

FAQ

What is CoCounsel?

CoCounsel is Thomson Reuters' legal AI platform, created through the acquisition of Casetext in 2023 for approximately USD 650 million. It is closely tied to the Westlaw database and is aimed primarily at US legal practitioners.

Where does CoCounsel store data, and why does that matter for Swiss firms?

CoCounsel processes data on Thomson Reuters infrastructure in the United States. For Swiss law firms, this is directly relevant under Art. 16-17 revFADP: disclosing personal data to the US requires either proof of an adequate protection level or one of the exhaustively listed exceptions in Art. 17 revFADP. Since the US does not have a general adequacy status under revFADP, the firm must justify the transfer on another ground - which creates compliance overhead and potential liability exposure under Art. 97 CO.

Where does CASUS store data?

CASUS hosts exclusively in Switzerland and the EU. No data is transferred to the US. The platform provides Zero Data Retention and no human review of uploaded documents. Details are on the security page.

Does CASUS cover Swiss case law?

Yes. CASUS searches over 660,000 cantonal and Federal Supreme Court decisions, as well as statutory law. Relevant reasoning sections are displayed directly in the answer, with no click-through to a separate system.

What does the FDPIC's 2024 AI guidance mean for law firms using AI tools?

The FDPIC clarified in 2024 that when AI services are used as processors, all data protection requirements must be extended fully to the AI provider, including transparency about sub-processors and storage locations. Firms using US-based tools must document this and be able to disclose it to clients. CASUS is hosted in Switzerland and the EU and does not use US sub-processors.

Does CASUS work inside Microsoft Word?

Yes. CASUS is available as a Microsoft Word add-in. Improvement suggestions from the Risk & Quality Review and Benchmark workflow, as well as Agent Mode changes, can be applied directly in the document - correctly formatted, without copy-paste.

What does CoCounsel cost?

Thomson Reuters does not publicly communicate pricing for CoCounsel. The subscription is typically tied to existing Westlaw contracts and aimed at enterprise customers. CASUS has no Westlaw lock-in; pricing and trial access are available at app.getcasus.com/signup.

What typical findings does the CASUS Benchmark workflow surface in NDA reviews?

In practice, the Benchmark workflow regularly flags: missing or inconsistent governing law clauses (relevant under Art. 116 PILA), divergent definitions of "Confidential Information" between Swiss and German templates, absent deletion obligations at contract end, and incomplete return-of-materials provisions. These are the points that tend to be missed under time pressure in manual reviews.

Is CASUS a complete alternative to CoCounsel?

For Swiss law firms and in-house teams working with German-language contracts and Swiss law, CASUS offers functionally broader and data-protection-compliant coverage. For US law and Westlaw integration, CoCounsel remains the more appropriate option. CASUS is not a US-market replacement - it is a more targeted solution for Swiss legal conditions.