Private restrictions are restrictions imposed by the seller or some prior owner on the grantee. Private restrictions are written and recorded in the courthouse. They pass with the land and bind all subsequent buyers.
Private restrictions are void if they are illegal even if they were legal when imposed. For example: Many deeds prior to the 1960's had race and religious restrictions in them. The restrictions are still in the deeds and are still recorded in the courthouse but cannot be enforced because they are illegal.