WASHINGTON, Jan. 22 -- The Peterson Institute for International Economics issued the following commentary on Jan. 21, 2026: * * * Can Trump legally apply tariffs on US allies over Greenland? By Alan Wm. Wolff (PIIE) The short answer, under international law, is no: The use of coercion to acquire another country's territory is forbidden. The question arises since President Donald Trump threatened on Saturday to impose new tariffs on several European countries unless Denmark sells Greenland to more PR