A U.S. trade court handed the Trump administration an initial victory March 6 by refusing to temporarily block controversial “global safeguard” tariffs as they apply to solar products from Canada.

The trade court rejected a request for an injunction or a restraining order to exempt solar cells or modules belonging to the plaintiffs, a group of Canadian solar manufacturers and U.S. importers. The case will continue, but in a bad sign for the companies, the court said they appear unlikely...