n. an attempt in a deed or will to prevent the sale or other transfer of real property either forever or for an extremely long period of time. Such a restraint on the freedom to transfer property is generally unlawful and therefore, void or voidable (can be made void if an owner objects), since a present owner should not be able to tie the hands of future generations to deal with their property. This ban on a restraint on alienation (transfer) is called "the rule against perpetuities." Examples: Oliver Oldtimer sells his ranch to his son with the condition that title may never be transferred to anyone outside of the family. Martha Oldtimer in her will gives her home to her daughter Jacqueline on condition that "Jacqueline's descendants must never sell the place." However, limiting transfer for a maximum period calculated by "lives in being, plus 21 years" is generally allowed. Restraints on alienation (so-called restrictive covenants) based on race ("only Caucasians may hold title") were declared unconstitutional in 1949. (See: convey, deed, rule against perpetuities, restrictive covenant)