Private citizens and corporations can absolutely do this, provided they're not discriminating against a protected class. A covenant or warranty on a deed are so

Private citizens and corporations can absolutely do this, provided they're not discriminating against a protected class. A covenant or warranty on a deed are some ways of doing this, but you can also just not sell. I think a bigger question in this instance is whether the government should be making these types of pseudo-moral decisions or if they should be bound by more restrictions than the average citizen/corporation.