Although Article I of the Constitution grants the legislature the exclusive authority “to lay and collect” tariffs, Section 232 of the Trade Expansion Act of 1962 gives this power to the president to protect “national security.”

Congress failed to define the term “national security,” however, leaving that determination to the president. Nor did Congress confine the available remedies, merely calling for such decisions to be made “in the judgment of the President.”

Why would Congress give away the farm? The 1962 law was passed at the height of the Cold War, when national security issues were paramount in national politics. Relative to now, lawmakers also harbored greater faith in presidential self‐​restraint.

In line with these expectations, previous presidents rarely tapped their Section 232 powers to impose import restrictions and never for a product other than petroleum.

Well, the Cold War ended, but the law remained on the books. Then Trump came along…

All Trump had to do was dust off the 1962 statute and, ultimately, issue a proclamation announcing the tariffs.

Federal law^[9], moreover, long has given the Secretary of Agriculture unfettered discretion to support virtually any farm commodity by tapping the Commodity Credit Corporation’s permanent, indefinite authority to borrow up to $30 billion from the U.S. Treasury^[10]. It’s essentially a revolving credit line: Congress annually replenishes this borrowing authority by appropriating funding to cover the Corporation’s net realized losses. While a portion of the $30 billion is dedicated by the Farm Bill, the remainder is available for discretionary use. During the Trump administration, the availability of these discretionary funds has averaged about $15 billion annually. All Trump had to do was order the Agriculture Secretary to start distributing money to “great patriot” farmers.

At the time it relinquished these powers, many decades ago, Congress was an entirely different institution^[11]. Back then, Congress tempered its delegations by competing with the president over how laws were implemented. That is, lawmakers from yesteryear jealously guarded the legislature’s institutional prerogatives. Over the last forty years, however, Congress has changed^[12], such that party loyalty now trumps institutional pride. So long as “their guy” occupies the White House, one political party—roughly half the legislature—loses interest in oversight. Neither party caucus in Congress seeks to claw back power from the presidency, because each wants its side to exercise executive authority.