“It’s putting tremendous stress on the system,” said Jennifer Hillman, a professor at Georgetown Law Center. “There are those who would go so far to say that the U.S. has almost effectively withdrawn from the W.T.O. by engaging in all the unilateral tariffs we’ve seen.”

Any decision could prove to be the undoing of the World Trade Organization, which the United States helped establish in 1995 as a forum to settle trade disputes and to set rules that keep commerce flowing freely around the globe. A ruling against the Trump administration could prompt the United States to leave the W.T.O. entirely. But siding with the United States’ claim of national security could also significantly diminish the organization’s authority and prompt other countries to begin citing their own national security interests to ignore inconvenient rules on topics like intellectual property, environmental standards or farm subsidies.

“If the United States has rewritten the rules of the W.T.O. system to say you can do anything you want if it’s in your national security interests, be prepared for every country in the world to come up with a new definition of what is its critical national security interest,” said Rufus Yerxa, the president of the National Foreign Trade Council and a former deputy director general of the World Trade Organization.

On Friday, the administration once again claimed national security when Mr. Trump decided to double the rate of tariffs on steel and aluminum imports from Turkey. In a statement, Wilbur Ross, the secretary of commerce, said that metal exports to the United States had not declined “to levels sufficient to remove the threat to national security” and that raising tariffs on Turkey would reduce that threat.