IEEPA, the International Emergency Economic Powers Act of 1977, is the US law that lets a president regulate international commerce after declaring a national emergency. Historically it powered sanctions: freezing assets, blocking transactions with hostile states. Its use to impose broad import tariffs is a modern innovation, and it matters because it bypasses the slower, evidence-based tariff processes Congress wrote for trade policy.
How IEEPA tariffs differ from normal tariffs
Traditional trade tools each require a process: Section 301 needs an investigation of unfair practices, Section 232 needs a national security finding, safeguards need an injury determination. Each takes months and produces a record that can be challenged. IEEPA requires only an emergency declaration, after which measures can arrive overnight and change just as fast. Speed and breadth are the point: entire trading relationships can be repriced in a single announcement.
Why markets struggle to price it
Markets can price a tariff schedule; they struggle to price a mechanism with no natural limits. Because IEEPA tariffs rest on emergency powers, their scope, duration, and legality are all uncertain simultaneously. Court challenges add a binary overlay: rulings can void entire tariff regimes retroactively, including refund questions worth tens of billions. The result is a risk premium that attaches not to any single tariff rate but to the unpredictability of the instrument itself.
What to watch
The legal track: appellate and Supreme Court rulings on whether IEEPA authorises tariffs at all. The escalation track: new emergency declarations extending coverage to fresh sectors or countries. And the negotiation track: tariffs imposed this way can be lifted as fast as they arrive, which makes de-escalation headlines as tradeable as impositions.