For several months, President Trump has been vandalizing the global economy and subverting the rules of international trade with his wrecking ball of tariff indiscretions. Finally, someone in Congress is doing something to stop this menace. Senator Bob Corker, a Republican from Tennessee, introduced legislation on Wednesday that takes back some of the authority President Trump has been abusing under the guise of protecting national security.

Mr. Corker, who is retiring, attracted six Republican co-sponsors for the bill, which would amend the Trade Expansion Act of 1962 to require the president to get approval from Congress for any tariffs proposed on national security grounds. But the Senate majority leader, Mitch McConnell, said he would not allow the legislation to come to the floor as a stand-alone bill. House Speaker Paul Ryan seems similarly uninterested in a bill likely to be vetoed by Mr. Trump. “You would have to pass a law that he would want to sign into law,” Mr. Ryan said. “You can do the math on that.”

Why don’t the president’s trade transgressions elicit meaningful resistance from party leadership? His trade views are disdainful of freedom and informed by economic fallacies, yet Republican leaders have watched quietly from the sidelines as Mr. Trump misappropriates his authorities to disrupt global supply chains, inflict pain on American trade partners, generate enormous amounts of domestic collateral damage and make the United States an international scofflaw.

The United States Constitution vests authority in Congress to collect duties and to “regulate commerce with foreign nations.” But over the course of the 20th century, Congress delegated some of its authority to the president. In most cases, the statutes giving the executive branch the authority to raise tariffs require that certain conditions be met and that any actions taken be subject to limitations, as well as judicial review.

President Trump has found a way to weaponize these statutes to advance his “America First” agenda. Since taking office, he has initiated six investigations under three highly contentious laws. Five of those investigations — on steel, aluminum, washing machines, solar panel components and Chinese technology products — have led to the president imposing or announcing tariffs on imports of more than 1,500 products valued at about $100 billion. A new investigation of whether imports of automobiles and parts constitute a national security threat could raise the value of sanctioned imports to $400 billion. Factoring in the likelihood of retaliation against American exporters, about 20 percent of total goods trade could find itself in the cross hairs by year’s end.

For more than 80 years going back to Franklin D. Roosevelt, American presidents viewed trade as a win-win proposition, fostering mutual economic growth and better relations among nations. Those presidents supported the rules and institutions that helped reduce protectionism and made trade more affordable, seamless and predictable. Between 1947 and 2006, average global tariffs fell to 4 percent from 40 percent in developed countries, trade flourished, and economies expanded rapidly.

Mr. Trump’s actions risk reversing these gains. He has invoked laws that were passed under the assumption that the president, reflecting a broader national consensus, would always be more circumspect and less likely to impulsively raise tariffs than a parochially minded Congress. Lawmakers failed to contemplate the possibility of a president as cavalier about the consequences of protectionism and as impervious to the lessons of history as Mr. Trump.

Last year, the excuse for the Republican leadership’s acquiescence to Mr. Trump’s trade assault was their desire for tax and regulatory reform. Done. Then the excuse was that opposing Mr. Trump on trade would invite a primary election challenge. With three months to go until the last state primaries, that concern is becoming moot. Loyalty to the president over the Constitution speaks volumes about a party that was once committed to free markets and the rule of law.

In fairness, a few Republican senators who aren’t retiring have shown some courage. Senator Mike Lee of Utah has proposed legislation that would effectively bring back to Congress most of the authorities it delegated to the executive over the years by requiring votes before any presidential trade proclamations can take effect. Senator Ron Johnson of Wisconsin is exploring how to give more legal weight to the arguments and concerns of American companies adversely affected by tariffs.

Mr. McConnell and Mr. Ryan have done nothing. At a minimum, they should be whipping up support for Mr. Corker’s bill to make sure they have two-thirds of both chambers ready to override Mr. Trump’s inevitable veto.

Republican leadership should also introduce “sense of the House” and “sense of the Senate” resolutions making clear that each chamber values the relationships America has with its allies and will work to repair and strengthen them. These measures are a promise to the American people and a signal to our allies that Congress will continue to support the global trading system and its rules and institutions, and that it will do all that is in its power to prevent the president from continuing to trample on both Republican and republican principles.