The United Nations is apparently demanding that we keep it illegal. …

Let’s keep a couple of things in mind. The treaties of the United States are just like other federal laws and regulations — they are the supreme law of the land, according to the Constitution’s Supremacy Clause. But there are treaties and there are treaties. Some treaties have immediate effect under domestic law (e.g., free-trade agreements) and are therefore considered “self-executing” treaties. But most treaties apply only to the U.S. government as a government, and are purely international in character even if they refer to domestic affairs. When these “non-self-executing” treaties apply to some aspect of domestic policy, they are no more than undertakings of the U.S. government to try to do this or that under its domestic laws.

The enforcement of international treaties that are “non-self-executing” is purely a matter of preserving national diplomatic credibility. But otherwise, any particular administration is perfectly free to stop observing any non-self-executing treaty, as part of the president’s authority to manage foreign policy.