AP has this story on the ruling, which appears to rely on the Purcell doctrine:

A federal judge on Thursday denied a request to block campaign finance provisions of a ballot measure approved by Alaska voters in 2020, finding that the plaintiffs had not demonstrated a likelihood of success on their outlined claims.

U.S. District Court Judge Sharon Gleason in a written ruling also said that in the context of elections, the U.S. Supreme Court has recognized that “‘lower federal courts should ordinarily not alter … election rules on the eve of an election.’” She said the plaintiffs “waited over one year to seek preliminary injunctive relief.”