On the merits, the Supreme Court’s decision last week to invalidate much of the president’s global tariff regime is to be welcomed. Yet the court’s judgment, sound as it might be on constitutional grounds, can’t by itself undo the damage that America’s turn to protectionism has already caused — nor prevent worse to come.

Avoiding further harm will be entirely up to the administration and Congress. Unless they choose to put stability first, things could quickly spiral toward a crisis.

By a 6-3 margin, the court found that the president had exceeded his authority when imposing a blizzard of high tariffs last year. It ruled that the law the administration had invoked, the International Emergency Economic Powers Act, didn’t explicitly authorize such measures when conferring the power to “regulate” trade. Other crucial questions were left unresolved, however, not least whether the White House can replace the tariffs using other legal tools or if it can keep on declaring so-called emergencies to justify expansive executive action.

Plans to replace the duties are already underway. In response to the ruling, the president said that he’ll impose a new global 15% tariff under Section 122 of the 1974 Trade Act and start investigations with a view to imposing more levies using different authorities. This leaves the outlook no clearer than before. In particular, firms that have paid the now-illegal tariffs will seek redress. Whether refunds will be granted and how they’d be administered has been sent back to lower courts — with some $170 billion of government revenue at stake.