The Kansas Republican Party’s chairman is demanding that Democrats’ last nominee for governor withdraw as an attorney from a federal lawsuit challenging voter registration policies.

GOP Chairman Kelly Arnold said Tuesday that former Kansas House Minority Leader Paul Davis’ involvement in the case filed last week violates state law.

Davis says he intends to proceed with the case.

Davis represents two northeast Kansas residents seeking to block enforcement of a 2013 law requiring new voters to provide proof of their U.S. citizenship to register.

They’re also challenging Republican Secretary of State Kris Kobach’s directive to counties to cancel thousands of incomplete registrations.

Arnold cited a state law preventing some ex-legislators from participating in such lawsuits unless they voted against the statute being challenged. Davis voted for the proof-of-citizenship law.