NEW YORK (Reuters) - New York's journalist shield law cannot stop a Fox News reporter from being forced to testify about her anonymous sources for a story on last summer's deadly mass shooting in Colorado, a divided state appeals court ruled on Tuesday.

Reporter Jana Winter cited two unnamed law enforcement sources when she said the accused gunman, James Holmes, sent a notebook with details about his plan to a psychiatrist before the attack that killed 12 and injured dozens more at a Denver-area movie theater.

Tuesday's 3-2 decision by a New York state appeals court means Winter can be compelled to testify in the Holmes case, but not necessarily forced to divulge the sources for her story. Under Colorado's weaker shield law, however, Winter could find it difficult to assert her legal privileges as a reporter.

The Reporters Committee for Freedom of the Press filed a friend-of-the-court brief in support of Winter that was signed by more than 40 news organizations, including Reuters.

"It's hard to say New York is such a good law when it leaves a reporter no remedy when another state wants his materials," said Gregg Leslie, the committee's legal defense director.

Winter's story appeared five days after the July 2012 shooting, for which Holmes is on trial for murder. Defense lawyers for Holmes believe authorities leaked the information to Winter in violation of a gag order and want to force her to reveal her sources so they can be sanctioned.

Winter, who is based in New York, is fighting a subpoena in both Colorado and New York compelling her to testify, saying that shield laws in those states protect her from having to name her sources.

On Monday, she made a brief court appearance in Colorado, where Arapahoe County District Court Judge William Sylvester extended the subpoena until a hearing next month on her motion to quash it.

Tuesday's ruling from the Appellate Division of the state Supreme Court in New York said that whether Winter can assert privilege to protect her sources was not relevant. It focused instead on whether she can be compelled to testify in general.

"Respondent is entitled to assert whatever privileges she deems appropriate before the Colorado District Court," Justice Darcel Clark wrote for the majority. "Compelling respondent to testify is distinguishable from compelling her to divulge the identity of her sources."

The dissenting judges, however, said that was a distinction without a difference.

"This approach ignores … the importance of our state's public policy in favor of protecting the identity of investigative reporters' confidential sources," Justice David Saxe wrote.

New York's shield law recognizes an "absolute" privilege for reporters' sources, Saxe said. In Colorado, a journalist can be required to reveal sources if a judge finds the interest of the party seeking the information outweighs First Amendment concerns, among other conditions.

Saxe said New York's stronger protections should be extended to Winter's case because it seems clear Judge Sylvester in Colorado will reject her privilege claim under that state's law.

Dori Ann Hanswirth, a lawyer for Winter, said she was "thrilled" that the court split 3-2, even though her side did not prevail. Under New York law, parties may appeal any 3-2 decision to the state Court of Appeals.

She reiterated that Winter will not reveal her sources under any circumstances, regardless of the outcome.

Daniel Arshack, who argued the case on behalf of Holmes, said the New York court had correctly decided the narrow issue of whether Winter can be required to appear as a witness in another state.

"The question of her right to protect confidential sources would be correctly determined by the court in which she is compelled to appear - in this case, Colorado," he said.

(Reporting by Joseph Ax; Editing by Cynthia Johnston and Philip Barbara)