President Donald Trump's threat to slap tariffs on Mexican imports didn't become reality, but it might have been enough to spur Congress into reclaiming some authority over trade.

A bill introduced this week by Sens. Tom Carper (D–Del.) and Tim Kaine (D–Va.), and Rep. Stephanie Murphy (D–Fla.) would place new limitations on two laws that currently allow presidents to unilaterally impose tariffs for supposedly "national security" purposes.

The legislation targets Section 232 of the Trade Expansion Act of 1962—which Trump invoked last year to impose tariffs on steel and aluminum imports under thinly justified national security grounds—and to tariffs imposed under the International Emergency Economic Powers Act, which Trump was intending to use against Mexico last month before backing down. Under the bill, presidents would retain the power to impose tariffs for national security reasons, but those tariffs would automatically lift after 120 days unless they receive congressional approval.

Lawmakers backing the bill say the effort is motivated by ongoing evidence that Americans are paying the price for Trump's tariffs, and by the administration's unprecedented threat against Mexican trade last month.

"Working families should not have to pay the price for the president's reckless use of this tariff authority," Murphy said in a statement. "The time has come for Congress to reclaim its constitutional authority over trade."

In Florida alone, consumers have paid about $600 million in higher costs due to tariffs, Murphy said, citing data from Tariffs Hurt The Heartland, a national pro-trade group that has been tracking the consequences of Trump's trade war. Nationally, the group estimates that tariffs have cost American consumers and businesses more than $27 billion.

Business and retail groups have lined up behind the legislation.

"At a time when American businesses and consumers are facing unprecedented tariffs imposed unilaterally, it's time to reexamine the appropriate balance on trade policy between Congress and the executive branch," said David French, vice president for government relations at the National Retail Association, in a statement.

The bill could be an important check against the White House's ongoing threats to hit imported cars and car parts with tariffs. The Commerce Department has provided the president with a framework for using Section 232 tariffs—by stretching the definition of "national security" to ridiculous lengths. Trump has so far declined to take action. Also noteworthy is Trump's seemingly out-of-nowhere announcement Wednesday that he could consider tariffs against Vietnamese imports.

The bill also provides an interesting political test for congressional Democrats, who have so far been content to criticize Trump's trade war without taking substantial action to stop it. Democrats on the campaign trail have also stepped up their criticisms of Trump's trade policies, but a recent survey by The Atlantic found that only one candidate (John Delaney) in the 25-person field favored getting America back into the Trans-Pacific Partnership—a good reminder that the political left remains as skeptical of trade as much of the Trumpian right.

Republicans in Congress have so far avoided a direct showdown with Trump over tariffs, though Sen. Chuck Grassley (R–Iowa) did convince the administration to lift its steel and aluminum tariffs on imported metals from Canada and Mexico. Other Senate Republicans have been sharply critical of Trump's tariffs, and a small group nearly revolted over last month's showdown with Mexico, which would have disrupted more than $670 billion in annual cross-border trade between the two nations

The new proposal joins a small pile of other bills making similar promises to rescind presidential tariff authority. Sooner or later, maybe Congress will finally get around to voting on a few of them.