It turned out, though, that Mr. Marshall’s Web sites had been put on a Treasury Department blacklist and, as a consequence, his American domain name registrar, eNom Inc., had disabled them.

This raises an interesting question. U.S. law prohibits U.S. persons from doing business with embargoed companies or persons. But what if that business primarily facilitates a speech activity? Does the first amendment supercede?

A Wave of the Watch List, and Speech Disappears - New York Times