The LePage administration says state lawmakers must appropriate funding before a voter-approved Medicaid expansion can be rolled out.
The court filing this week says the Legislature must act because a statewide referendum did not specify where the money to expand Medicaid would come from.
Groups that support the Medicaid expansion sued after the administration missed an April 3 deadline for an application to receive an additional $525 million in annual federal funding. The LePage administration contends the deadline doesn't commence until money is appropriated.
A judge has scheduled arguments on the lawsuit later this month.
LePage has long opposed Medicaid expansion. He contends it would cost state taxpayers $50 million in fiscal year 2019 and necessitate hiring 100 workers at a cost of more than $2 million.