Under the International Emergency Economic Powers Act (IEEPA), presidents can impose, modify, or waive sanctions after declaring a national emergency. Short-term waivers can ease energy or financial shocks, but they also sidestep congressional preferences and change leverage in conflicts; oversight depends on National Emergencies Act reporting and periodic renewal votes that Congress seldom takes.
Examples include temporary waivers to allow limited oil purchases from sanctioned states during crises, similar to 30-day relief windows granted amid wartime price spikes.