A hallmark of the Trump administration is that it resorts to the "national security" exemption to force trade partners to the negotiating table. Insisting that economic security is national security allows Washington to impose unilateral sanctions that would otherwise be banned by bilateral and multilateral trade agreements. But the United States is using an expansive definition of that term that has virtually no limits; if any job lost is a threat to national security then the exemption has no real meaning. This approach poses a fundamental challenge to the international trade order. Legitimation and embrace of the approach by other countries could bring about its collapse.
The claim that there are circumstances in which national security concerns can trump the preference for free trade makes sense. There are goods and commodities that are essential to national defense and whose supply should be assured or their distribution controlled. Moreover, a strong economy is a critical component to the strength of a nation and its ability to defend itself.
But there are limits to that logic. Some goods are truly vital to national defense; others are peripheral. A strong economy matters, but "strength" is relative and depends on the time frame. The accelerating pace of economic change means that technologies or commodities considered essential may change over time. The national security exemption could be abused to include anything that might at some time become important. Such a claim would swallow the entire trade system.