A judge in Northern California is set to hear arguments over whether to block a new federal law that requires sex offenders to have "unique identifiers" in their passports.

U.S. District Court Judge Phyllis Hamilton has scheduled a hearing Wednesday in Oakland on a nonprofit group's request for a preliminary injunction against the so-called International Megan's Law, which President Barack Obama signed into law in February.

The law requires the government to add a mark to the passports of registered sex offenders and for foreign nations to be notified that some registrants intend to travel there.

The group, California Reform Sex Offender Laws, filed a lawsuit challenging the law a day after Obama's approval.

It says a symbol on a passport identifying people as registered sex offenders violates their constitutional rights and puts them and others traveling with them in danger, including family members and business colleagues.

"For the first time in the history of the United States, American citizens will be forced by the government to label and stigmatize themselves on a document foundational to citizenship," the lawsuit filed Feb. 8 reads.