Wyoming Governor Mark Gordon on Tuesday said Washington state has acted unconstitutionally in preventing construction of a coal export terminal that would send Wyoming coal to customers in Asia.

The governor earlier in the day said Wyoming will join Montana in asking the U.S. Supreme Court to hear a challenge to Washington state's refusal to certify the coal terminal project on environmental grounds. Gordon argues that Washington's decision amounts to regulating interstate commerce, which he says is clearly a role reserved for the federal government rather than individual states.

The Washington Department of Ecology in 2017 denied permit applications to build the proposed export terminal in Longview, Washington, citing section 401 of the federal Clean Water Act.

Gordon says that decision amounts to a de facto embargo on Wyoming and Montana coal, an action that he says is unconstitutional.