CVS and Express Scripts filed lawsuits on Thursday seeking to overturn an Arkansas state law set to go into effect next year that would ban pharmacy benefit managers from owning pharmacies. The law puts an unconstitutional restriction on interstate commerce by burdening out-of-state companies like Express Scripts,

CVS and Express Scripts asked a federal judge on Thursday to block a law prohibiting pharmacy benefit managers from owning or operating pharmacies in Arkansas, challenging the first such restriction enacted by a state.

Express Scripts and CVS Pharmacy — two of the three biggest U.S. pharmacy benefit managers — are suing to block an Arkansas law that forbids PBMs from owning pharmacies. The PBMs say the law is a form of economic protectionism that violates the U.S. Constitution by using curbs on out-of-state companies to help companies in Arkansas.