Originally Posted by vranasaurus
...Isn't judicial enforcement "state action" and then one could argue that such ion in violation of the covenant is unconstitutional?...
I seriously doubt it. Any contract involves trading one or more rights for whatever benefits you hope to derive from the contract. Some of those rights might even fall into the otherwise "constitutionally protected" category.
Many contracts contain confidentiality clauses. Various types of nondisclosure agreements are common in certain contexts. These impair one's free speech, but they are enforceable. The very nature of a contract is that you trade something, or usually a number of things, for something you want. And those trades are enforceable.
There are some narrow exceptions. A contract with an illegal object is not enforceable, so I could enforce you agreement, if you're my competitor, to fix prices. An contract the performance of which requires an illegal act, e. g., committing murder, is unenforceable.