You are correct, but the way he applied it was illegal. He can apply it according to law instead of making up some emergency wartime declaration thingy.
SUPREME COURT SAID I CAN’T DO TARIFFS; SO I’M GOING TO IMPOSE EVEN MORE TARIFFS BECAUSE THE SUPREME COURT THAT I MOSTLY APPOINTED IS ILLEGITIMATE AND THEIR INSUBORDINATE GALL IS BORDERING ON INSURRECTION