Before the New York Rangers and Toronto Maple Leafs duked it out on the ice, Blueshirts fans at Madison Square Garden booed the Canadian national anthem.

Fans in Canada have been booing the American anthem at NHL and NBA games since Donald Trump took office. The gesture is in response to the president’s threats of tariffs and continued suggestion that he could use economic coercion to make Canada “the 51st state.” It gained more attention because of the nation-vs.-nation showdowns in the 4 Nations.