Feb 11 (Reuters) - A federal judge in Delaware on

Tuesday said that a former competitor of Thomson Reuters ( TRI )

was not permitted by U.S. copyright law to copy the

information and technology company's content to build a

competing artificial intelligence-based legal platform.

U.S. Circuit Judge Stephanos Bibas' decision against defunct

legal-research firm Ross Intelligence marks the first U.S.

ruling on the closely watched question of fair use in AI-related

copyright litigation.

Fair use is a principle that allows the unauthorized use of

copyright-protected works under certain circumstances. The legal

theory represents a key defense for tech companies including

OpenAI, Microsoft ( MSFT ) and Meta Platforms ( META ) in a

series of copyright cases brought by authors, record labels,

visual artists and others over the use of their material to

train AI systems.

Tech companies argue that generative AI systems make fair

use of copyrighted material by studying it to learn to create

new content, while copyright owners say the companies use their

work to generate competing content that threatens their

livelihoods.

A Thomson Reuters ( TRI ) spokesperson welcomed the decision. "We

are pleased that the court granted summary judgment in our favor

and concluded that Westlaw's editorial content, created and

maintained by our attorney editors, is protected by copyright

and cannot be used without our consent. The copying of our

content was not 'fair use,'" the company said in a statement.

Thomson Reuters ( TRI ) is the parent company of Reuters News.

Attorneys and spokespeople for Ross did not immediately

respond to requests for comment.

Bibas reconsidered his previous decision that determining

fair use should be left to a jury at a trial on Thomson Reuters' ( TRI )

copyright infringement claims against Ross.

"I studied the case materials more closely and realized that

my prior summary-judgment ruling had not gone far enough," Bibas

said on Tuesday.

The judge determined that a jury should still consider the

underlying case.