For the second time in less than a year Canada has invoked a 1977 Pipeline Treaty with the United States to prevent the closure of Enbridge's Line 5 pipeline in Wisconsin.

The Bad River Band, a Native American tribe in northern Wisconsin, wants the 1953 pipeline shut down and removed from its reservation because of the risk of a leak and expired easements, which are land use agreements between Enbridge and the tribe.

But last May, Enbridge filed a motion in a U.S. district court saying federal law prohibits attempts to stop the pipeline's operations. The motion sought to dismiss some of Bad River Band's claims.

The company said it remains committed to resolving the dispute amicably and has proposed re-routing the Line 5 pipeline around the Indian reservation.

The 1977 pipeline treaty governs the free flow of oil between Canada and the United States, and last year Canada invoked it for the first time ever to start negotiations with U.S. to resolve a dispute with Michigan state, which wants to shut down Line 5 on environmental grounds.

This month, a U.S. judge sided with Enbridge in ruling that a federal court should hear a suit by the state of Michigan seeking to force shutdown of the pipeline underneath the Straits of Mackinac in the Great Lakes.