Donald Trump has been able to weaponize tariffs by citing a section of the International Emergency Economic Powers Act (IEEPA) that allows a president to “regulate … importation”. As long as tariffs were presumed to be a permissible form of “regulat[ing] … importation” under this law, Trump could assert the power to unilaterally impose whatever tariffs he wanted, at whatever product-by-product levels he chose, and with any exemptions he desired – all without explanation or explicit authorization from Congress.