Sacramento County Superior Court Judge Timothy Frawley upheld a title that says the measure, Proposition 8 on the Nov. 4 state ballot, "eliminates the right of same-sex couples to marry."
Frawley wrote that the title was not false, misleading or argumentative.
"The attorney general's title is an accurate statement of the primary purpose and effect of the measure," the judge said.
He turned down a request by initiative proponents for removal of the title.
The proponents said they plan to appeal immediately.
Attorney Andrew Pugno said, "We believe the attorney general has attempted to influence voters against the measure. It is our goal to ensure that voters have a fair opportunity to decide this measure for themselves on Election Day."
Brown issued a statement saying, "This lawsuit was more about politics than the law. The court properly dismissed it."
The case could be appealed both to a state appeals court in Sacramento and then to the California Supreme Court. But Secretary of State Debra Bowen and State Printer Geoff Brandt have asked that the courts complete all rulings by 5 p.m. Monday to allow time for printing and distributing ballot pamphlets.
If passed, the initiative would amend the state Constitution to provide that "only marriage between a man and a woman is valid or recognized in California."
The measure would overturn a May 15 decision in which the California Supreme Court said the constitution gives gay and lesbian couples a right to marry.
The title with the word "eliminates" was added to the ballot wording by Brown after the high court ruling. The attorney general is required under state law to prepare "true and impartial" titles and summaries of ballot measures.
The summary that will appear in voters' ballot pamphlets continues to contain a second sentence that tracks the actual wording of the proposed amendment, saying that only marriage between a man and a woman would be valid or recognized.
Initiative proponents argued that Brown's title was argumentative because the word "eliminates" is a strongly negative, active verb.
Bur Frawley wrote, "There is nothing inherently argumentative or prejudicial about transitive verbs, and the court is not willing to fashion a rule that would require the attorney general to engage in useless nominalization."
In a second ruling in a lawsuit filed by initiative opponents, Frawley ordered a change in the wording of a ballot argument by supporters of the measure.
He said the language should be changed to say that state law may require, rather than will require, public schools to teach children as young as kindergarteners that there is no difference between gay marriage and traditional marriage.
Geoff Kors, a lawyer for two same-sex marriage advocates who challenged the argument's wording, said that while his clients had asked to have the entire sentence removed, they won't appeal.
Kors said, "We are delighted that the court found some of the proponents' arguments to be false and misleading. We are confident that California voters will see through these scare tactics."