What it does The memorandum opinion revises portions of the court’s 2023 summary-judgment ruling under Federal Rule of Civil Procedure 54(b). It finds the Westlaw headnotes and Key Number System sufficiently original for copyright protection, determines that Ross’s Bulk Memo questions actually copied and are substantially similar to 2,243 headnotes, and rejects Ross’s innocent-infringement, copyright-misuse, merger, and scènes à faire defenses. The court grants Thomson Reuters summary judgment on fair use after weighing the commercial, non-transformative purpose of Ross’s copying and its likely effect on legal-research and AI-training-data markets. Remaining factual issues include whether particular copyrights remain valid or timely and other claims not addressed in the opinion.

Who it affects The ruling directly affects Thomson Reuters, West Publishing, Ross Intelligence, and LegalEase, whose Bulk Memos supplied approximately 25,000 training examples. It concerns companies developing legal-research or AI products from copyrighted editorial content, especially where the copied material is used at an intermediate training stage rather than shown in the final output.

Why it matters The decision treats copying written editorial material to build a competing, non-generative AI legal-research tool differently from intermediate copying of computer code for interoperability or access to unprotected functionality. It also recognizes potential markets for licensing legal-research data to train AI systems.

Key dates and numbers

• February 11, 2025: memorandum opinion filed.
• Case No. 1:20-cv-613-SB; Document 770.
• 2,243 headnotes: summary judgment granted on copying and substantial similarity.
• Approximately 25,000 Bulk Memos: supplied to Ross by LegalEase.
• 80% initial training and 20% later validation: Ross’s stated use of the Bulk Memos.