WASHINGTON, June 14 -- Donald Trump's signature 10 percent global tariff is living on borrowed time and a temporary court order. The Supreme Court has already told him that the law he first invoked to impose it does not permit it. A federal trade court has now said the same thing about his backup legal theory. Twenty-four states are suing to kill the tariff outright. The only reason it is still being collected at American ports, and still adding to the price of imported goods, is a short-term stay from an appeals court that has paused the latest defeat while it makes up its mind. This is not a policy standing on solid legal ground. It is a policy being kept alive by procedure.

The story of how the tariff got here is a study in refusing t...