DONALD TRUMP claims to like free, fair and smart trade. It is precisely for that reason, he says, that he doesn’t like the rules under which America trades: “I’m not sure that we have any good trade deals.” The current dispensation allows imports to eviscerate American employment and unfair barriers abroad to stymie American exporters. Time to even things up; time to move towards reciprocity.

Mr Trump is hardly the first president to complain about trade deals. Barack Obama criticised the North American Free-Trade Agreement (NAFTA) during his campaign to be president, then negotiated an upgrade while in office, the doomed Trans-Pacific Partnership. Mr Trump’s plans for a huge renegotiation of NAFTA are arguably an escalation rather than an absolute departure. The depth of his suspicions of the World Trade Organisation (WTO) looks like a fundamental shift.

The WTO is a pact with 163 other countries, setting out tariff commitments and offering a forum to settle trade disputes. There are three discernible reasons for the Trump administration’s dislike of it. The first is that 77% of America’s trade deficit stems from trade with countries that trade with America under WTO rules. The second is that America’s tariff commitments under the WTO are indeed lower than other countries’. In 2015 America applied an average tariff of 3.5%, compared with 4.0% for Japan, 5.1% for the EU and 9.9% for China. (The highest average, 34%, belongs to the Bahamas.) That sort of thing is pretty hard to square with Mr Trump’s vision of reciprocity. And the third is a suspicion that WTO rules prevent America from cutting “good” deals with other countries.

America’s trade deficit is a poor indicator of the success of the WTO. In June 2016 the United States International Trade Commission, an independent American agency, assessed current and past research on the benefits of membership; the evidence suggested that it boosts trade flows between 50% and 100%. That means bigger markets for American exporters and cheaper stuff for shoppers, as well as healthy competition.

The issue of non-reciprocal access is more complex. The WTO works according to the “most-favoured nation” principle introduced to American trade policy by Franklin Roosevelt in 1934. The idea is that if a country reduces a tariff imposed on goods from another country, it will do the same for all the other partners in the trade deal. The principle was supposed to make cutting deals easier: when signing a deal, trade partners could feel safe that they were not about to be undercut by a slightly lower tariff elsewhere. It was also meant to avoid the resurgence of anything like Britain’s exclusionary policy of “Imperial preference”, which had been used to carve out trade blocs in a way that kept America out.

When Roosevelt was crafting this policy, tariffs were eye-wateringly high. In the second half of the 20th century, tariffs were reduced with the aim of luring other countries away from the influence of communism. The most-favoured-nation principle meant that, as the WTO expanded, some new entrants could benefit from trade liberalisation without doing much tariff-cutting themselves—what trade economists call the latecomer’s advantage. When China formally entered the WTO in 2001, it could benefit from tariffs between the EU and America that had been haggled downwards for decades.

The WTO’s most-favoured-nation principle means that America cannot raise its tariffs against countries that impose high tariffs on it, as Wilbur Ross, Mr Trump’s commerce secretary, has suggested it logically should. And it does indeed leave America with fewer concessions to offer when striking new deals.

There are real drawbacks to the current multilateral trading system. The WTO system of settling disputes is slow; getting new rounds of tariff cuts through seems practically impossible. But these drawbacks are quite unlike the restraints it places on the sort of muscular reciprocation Mr Trump’s team contemplates. Those restraints are not failures: they are part of the point of the pact.

In the best case, the threat of a reciprocal tax or tariff might force another country or countries to lower their tariffs. Perhaps Mr Trump could squeeze the tariff on car imports to China, currently 25%, down to the level on car imports in America, currently 2.5%, on the back of a credible threat to abandon the WTO. It could work to clamp down on common gripes about, for example, China’s habit of dumping its excess capacity on global markets. The Trump administration is currently mulling over whether imports of steel and aluminium are a threat to national security, for example.

Over the edge

But there is a limit to the stress that the WTO can take. The system is designed to put up with disputes; if one country breaks the rules, then others can retaliate, but only by enough to compensate them for the damage. It is not designed to deal with disregard for the norms on which it is based, including the most-favoured-nation principle, spreading from one very big economy to the world at large. If other countries interpret Mr Trump’s trade policy as abandonment of the WTO, all hell could break loose. By trashing such norms, the world could descend into the sort of tit-for-tat trade war that Roosevelt was trying to fix. If Mr Trump’s foreign relations degenerate into acrimonious protectionism, then American shoppers and workers will lose. What constrains America now constrains other countries, too.