The racial-covenant case (Shelley v. Kraemer) is actually interesting for the departure from normal constitutional questions -- typically a court either upholds

The racial-covenant case (Shelley v. Kraemer) is actually interesting for the departure from normal constitutional questions -- typically a court either upholds the constitutionality of a statute, or rules the statute unconstitutional and thus unenforceable. In Shelley, effectively the court ruled that racial covenants, which were private contracts, were perfectly legal, perfectly constitutional and perfectly valid, but that the state government (which would normally enforce this type of contract) could not enforce racial covenants because doing so would require actions outside the powers of the state government. Which comes back to whether either a state government or the federal government could enforce certain types of gag-order provisions in contracts, since the required action might similarly be outside the powers of the government.