A federal trial challenging a state law that will require petition circulators to register is getting under way today in Aberdeen.

The lawsuit, filed by the grassroots organization SD Voice, seeks an injunction to stop the law from taking effect next July. It requires petition circulators to apply with the secretary of state for an identification number and be included in a directory. SD Voice says the law is unconstitutional.

The plaintiffs say the law places additional restrictions on ballot measures, but makes no changes to the process related to candidates, candidate committees, political action committees or political parties.