As the sites have increased, legal scholars and women’s advocates have begun to push for criminal penalties for people who post on them. Only New Jersey has a law that would allow for criminal prosecution, although it was not written with revenge porn in mind.

But proposals have met opposition from critics who worry that such laws would infringe on the First Amendment. A bill addressing the issue failed in the Florida Legislature this year.

And even California’s law, which on Monday was awaiting Gov. Jerry Brown’s signature, would make only some forms of revenge posting a misdemeanor punishable by jail time or a hefty fine — applying only to photos taken by others and posted with an intent to cause serious distress.

“It has been watered down again and again as it has weaved its way through Sacramento,” said Charlotte Laws, who began pushing for legislation after pictures of her daughter, Kayla, 26, were posted on a site.

“What we really need is federal legislation,” Ms. Laws said.