At least four Medicaid recipients have filed a class action lawsuit that challenges the legality of a new Medicaid law.

The controversial measure, scheduled to take effect Saturday, would require more than 53 million Medicaid recipients to prove their citizenship to receive benefits. The suit claims that the law unnecessarily requires current enrollees who have already been declared eligible for Medicaid to prove their citizenship again.

Long-term care providers are concerned that residents who are mentally impaired may not be able to provide required documentation. Other opponents contend that scant proof exists to show illegal immigrants have been signing up for Medicaid services.