Legally, it's not hard, you just make a law. You can make an existing type of contract illegal. At that point in time, the contract (or parts of it) become unen

Legally, it's not hard, you just make a law. You can make an existing type of contract illegal. At that point in time, the contract (or parts of it) become unenforceable. See banning non-competent agreements. See https://en.wikipedia.org/wiki/Shelley_v._Kraemer https://en.wikipedia.org/wiki/Shelley_v._Kraemer where the United States Supreme Court ruled the 14th amendment made "racially restrictive covenants" unenforceable. Also, depending on the state, you might be able to get a covenant removed by a court if it has been violated for a sufficient period of time.