NEW ORLEANS (AP) — A federal judge has refused to throw out a court challenge to a Louisiana law that has required people convicted of soliciting oral or anal sex to register as sex offenders.

U.S. District Judge Martin Feldman ruled that the challenge raises a plausible argument that the law violates the Constitution’s equal protection clause.

The law targeted people arrested for soliciting oral or anal sex for money. They can be charged with prostitution or a crime against nature. If convicted of a crime against nature, they have been required to register as sex offenders. A prostitution conviction doesn’t require such registration.

Feldman’s ruling did throw out parts of the challenge. Gov. Bobby Jindal was dismissed as a state defendant because he has no role in enforcing the law. The judge also rejected claims that the law violates the challengers’ due process rights.

The state Legislature amended the law this year. Now, anyone convicted of a “crime against nature by solicitation” no longer will be required to register as a sex offender.

But the change doesn’t apply to roughly 400 people who already have been convicted of the crime and are registered sex offenders, according to Davida Finger, a Loyola University law professor.

The plaintiff is an anonymous group of those registered sex offenders.

Feldman’s Wednesday decision keeping the challenge alive was praised in a joint news release by two equal rights groups, the Center for Constitutional Rights and Women with a Vision, who called the law discriminatory. Critics of the law have long said it is used to target gay and transgender people.

“Our clients have been labeled as sex offenders simply because they were convicted of crime against nature by solicitation rather than prostitution — which encompasses exactly the same conduct,” attorney Alexis Agathocleous of the Center for Constitutional Rights said.

Deon Haywood, executive director of Women with a Vision, echoed longstanding complaints that the law in question has been used to target gays.

“The women and transgender women of our NO Justice Project have been living with the scarlet letter of ‘sex offender’ status for years,” said Deon Haywood, executive director of Women with a Vision.

Copyright 2011 The Associated Press.