There is concern among trade experts that President Donald Trump’s plan to impose tariffs on foreign steel and aluminum may eventually give the administration an excuse to walk out of the World Trade Organization entirely.

It is not difficult to sketch out a scenario where the Trump administration would just say “that’s it, we are leaving,” said Jennifer Hillman, a fellow at the Institute of International Economic Law at Georgetown University, on a conference call with reporters sponsored by the Atlantic Council.

Trump is planning to justify the sweeping tariffs on the grounds that the foreign imports threaten national security.

Foreign government are likely to quickly go to the WTO and ask that the tariffs be ruled illegal.

Hillman said the U.S. may counter by saying it was taking the action under Article 21 of the General Agreement on Tariffs and Trade, which Hillman called the untested “third rail” of trade laws. Essentially, the article says that some binding tariff agreements can be broken during wartime.

Read:Why a full-blown Trump trade war probably won’t happen

The Trump administration has indicated, in its comments on a dispute between Qatar and the United Arab Emirates, that it believes once Article 21 is invoked, a WTO panel has no authority ”and should pack up and go home,” Hillman said.

“I don’t know whether the rest of the [WTO] members are ready to go along with that. The implications are very significant,” Hillman said.

The WTO panel might rule anyway, setting up a standoff.

This suggests to some that the whole reason to go down the national security route is really to create a crisis so the U.S. can withdraw from the WTO, Hillman said.

Experts said the Trump administration is essentially arguing that Article 21 is self-judging. A country gets to decide what is essential to national security.

Grant Aldonas, who served as undersecretary for international trade in the Commerce Department during the Bush administration from 2001 to 2005, said he was worried that the Trump White House argument would just open the door for China and other countries to justify trade protections on national security grounds.

Aldonas said the Bush White House explored using national security grounds to justify steel tariffs in 2001 but “we concluded there was absolutely no evidence imports of steel are threatening national security.”

“The industry is doing much better than in 2001. Indeed, demand is rising as a result of economic growth at home,” he said. Most defense weapons, like drones, are made of composites, he added.

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“The action [on national security grounds] is pretty clearly unjustifiable,” and is “challengeable” in U.S. courts, Aldonas said.

Any U.S. court is likely to consider the president’s tweets to see whether the administration acted in accordance with the statute, he noted.