Iran and the United States have made bold statements about the Strait of Hormuz. Iran says it has the right to police it, demanding fees from transiting ships to pay for reconstruction from an illegal war. The U.S. says it has a right to blockade it, cutting off Iran from lucrative sea lanes in its own waters.

But what does international law say? And what might this all mean for the shipping lanes crucial to global commerce going forward?

Experts debate some of the details. But most agree Iran is overstepping its rights in one way or another, and that the conclusion reached by the U.S. and Iran will be of enormous consequence.…