Once of the first women to accuse him, Judd claims that in 1998, Weinstein defamed her and damaged her career by telling "Lord of the Rings" director Peter Jackson that she was a "nightmare" to work with.
U.S. District Judge Philip S. Gutierrez said it was unclear if Judd's harassment claim fell under the definition of her lawsuit. But the judge ruled that lawmakers had "modified, rather than clarified" the 1999 law, making it inappropriate to apply its new standards retroactively.
Representatives for Ms Judd and Mr Weinstein could not immediately be reached for comment on the ruling.
But he said Ms Judd may proceed to trial with separate allegations against Weinstein of defamation and economic interference, according to reports in the Los Angeles Times and The New York Times.
Ashley Judd arrives for the 90th Annual Academy Awards on March 4, 2018, in Hollywood, California. But the judge also said Judd can pursue her accusation that Weinstein tried to ruin her career after she rejected his advances. It even acknowledged that the common meaning of the words in the statute would encompass her professional relationship with Mr. Weinstein.
The judge said he was not determining whether Judd was sexually harassed by Weinstein "in the colloquial sense of the term".
But Judd alleged that she proposed the pact to elude Weinstein after he invited her to his Beverly Hills hotel room.
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About a year after the alleged incident, Judd said she was seriously considered for a role in the "Lord of the Ring" trilogy, which she didn't get.
"The burden on Weinstein has the potential of being dramatically and unfairly negative if the stay is denied".
Despite the setback, Judd's lawyer remains confident that the actress will prevail in her three remaining claims.
Weinstein's attorney in this case, Phyllis Kupferstein said in a statement to CNN, "We have said from the beginning that this claim was unjustified, and we are pleased that the court saw it as we did".
Judd appeared in "Frida", which was distributed by Weinstein's company Miramax in 2002, and starred in "Crossing Over", which was distributed by The Weinstein Company in 2009. Dozens of women have accused Weinstein of rape and sexual misconduct that allegedly took place over decades.
The former movie mogul has denied engaging in non-consensual sexual activity.
Weinstein is to stand trial in May in NY on five charges - these include rape involving two other women.