Terms trackerLegal tech platforms

Westlaw (Thomson Reuters) Terms of Service — Key Clauses & Change History

Westlaw is the market-leading legal research database, now deepening its AI footprint through CoCounsel Legal (agentic AI + deep research), a strategic alliance with Anthropic (Claude), OpenAI (GPT), and Google (Gemini), and a proprietary "Thomson" LLM slated for summer 2026. Thomson Reuters intentionally blocks crawlers on its public TOS page — which means monitoring requires active surveillance. DriftPatrol tracks legal.thomsonreuters.com/en/policies/terms-and-conditions and surfaces changes the day they happen.

Thomson Reuters blocks automated crawlers on its TOS page. DriftPatrol uses rendering-based monitoring to detect changes the public web misses. 40+ changes documented since Jan 2023.

Current terms at a glanceEnterprise agreements govern; public TOS is a floor

Provision	What it says	Why it matters
AI Training	Zero-retention APIs; sub-processors prohibited from training on customer data	Thomson Reuters contractually prohibits its AI sub-processors (Anthropic, OpenAI, Google) from training on customer data. Zero-retention API design for CoCounsel queries — no input stored. Strongest AI training protection among the major legal research platforms alongside Harvey. Strong
AI Providers	Anthropic (Claude), OpenAI (GPT), Google (Gemini) — plus proprietary "Thomson" LLM in 2026	Three external AI providers named. Proprietary LLM (summer 2026) will reduce dependency on third-party providers but introduces new governance questions about training data sources. Monitor the TOS for addendum language when the Thomson LLM launches. Watch
Data Retention	Configurable at organization level; zero-retention API design for AI queries	Enterprise customers can configure retention periods. Zero-retention is the default for CoCounsel AI queries — but confirm your specific contract, as this may require a negotiated addendum on older agreements. Verify
Governing Law	Not public — negotiated per enterprise agreement	Public TOS does not state governing law. Enterprise agreements typically specify Ontario or New York law. If your firm signed pre-2020, your governing law clause may not address AI features at all. Request an updated addendum. Gap
Arbitration	Not public — enterprise agreements negotiated	No standard arbitration clause in public TOS. Enterprise agreements vary. Firms signing new deals should negotiate explicit dispute resolution covering AI feature failures, which are not addressed in legacy contracts. Gap
Liability / Indemnification	Not in public TOS — enterprise agreements govern	Enterprise liability and indemnification terms are deal-specific. The Feb 2025 ROSS litigation (Westlaw headnotes copyrightable; AI training not fair use) has reinforced TR's enforcement posture. Ensure your firm's AI use of Westlaw content is expressly authorized in writing. Risk

Documented changes40+ changes since Jan 2023 · Rendering-based monitoring

Apr 26, 2026 — Most recent detected change

legal.thomsonreuters.com/en/policies/terms-and-conditions · Content update detected

Most recent of 40+ documented changes since Jan 2023 DriftPatrol flagged for human review. Clause-level diff pending AI-assisted analysis for monitored subscribers.

Mar 2026 — "Thomson" Proprietary LLM Announced

Thomson Reuters public announcement · Proprietary LLM · Summer 2026 launch

+ "Thomson" proprietary LLM announced for summer 2026 deployment + Intended to reduce dependency on Anthropic, OpenAI, and Google sub-processors flagged: AI providers, training data, TOS addendum impact: Proprietary LLM will require updated AI governance disclosures in TOS and DPAs. Watch for new addendum language Q2–Q3 2026. The question to ask: what data was used to train the Thomson LLM, and does your subscription data fall within that scope?

Jan 2026 — CoCounsel Expands to UK

Thomson Reuters product update · CoCounsel UK rollout

+ CoCounsel Legal agentic AI platform launched for UK law firms flagged: UK GDPR, cross-border data, sub-processor impact: UK deployment triggers GDPR Article 46 transfer mechanism obligations. Confirm your DPA covers UK data flows under the UK International Data Transfer Agreement (IDTA) — not just EU Standard Contractual Clauses.

Sep 2025 — ROSS Appeal Affirmed

Federal Circuit — ROSS Intelligence appeal · Westlaw headnotes copyrightable

Westlaw v. ROSS Intelligence — appeal of Judge Bibas Feb 2025 ruling + Federal Circuit affirmed: Westlaw headnotes and key numbers are copyrightable + AI training on licensed Westlaw content is NOT fair use — as a matter of law flagged: copyright, AI training, license scope impact: Any law firm or legal AI vendor using Westlaw content — headnotes, key numbers, annotations — to train or fine-tune AI models is now exposed to copyright liability. This is binding Federal Circuit precedent. Audit your AI workflows against your Westlaw license scope immediately.

Aug 2025 — CoCounsel Legal Launch

Thomson Reuters product update · CoCounsel Legal agentic AI

+ CoCounsel Legal launched — agentic AI with Deep Research mode + Existing subscribers auto-upgraded via SaaS delivery model flagged: auto-upgrade, AI features, consent impact: If your firm did not explicitly opt into AI features, you may have received them automatically. Review your subscription terms for AI feature opt-in/opt-out language — and confirm your client data policies cover AI-assisted research workflows.

Feb 2025 — ROSS Ruling + Major TOS Expansion

legal.thomsonreuters.com/terms · Significant content addition · ~15KB → ~20KB

+ AI governance provisions substantially added — largest single content jump since monitoring began + Zero-retention API language codified for AI query processing + Sub-processor prohibitions on training expanded Concurrent: Judge Bibas ruled Westlaw headnotes copyrightable; AI training not fair use flagged: AI governance, zero-retention, training prohibition impact: The Feb 2025 dual event — TOS expansion + ROSS ruling — represents the most significant shift in Westlaw's IP and data governance posture in a decade. Firms negotiating enterprise renewals after Feb 2025 should have these provisions expressly incorporated by reference.

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Tracked URL: legal.thomsonreuters.com/en/policies/terms-and-conditions · 40+ changes since Jan 2023 · Last detected: Apr 26, 2026 · Informational only — not legal advice.