A more thorough explanation:

Definition: Restraint on alienation is a legal restriction that prevents the transfer of ownership of a property. This restriction can be indefinite or for a fixed period of time and is usually found in a deed or will.

However, courts generally do not like restraints on alienation because they limit the ability of future generations to own and use the property. Therefore, restraints on alienation are only upheld if they are not unreasonable.

For example, in the case of Shelby v. Kramer, the U.S. Supreme Court struck down a provision in a conveyance that stated "only Caucasians may hold title" because it violated the Equal Protection Clause. This is an example of an unreasonable restraint on alienation.

Another example is the common law rule against perpetuities, which limits the time period for restricting the transfer of property title to lives in being, plus 21 years. This means that a property owner cannot restrict the transfer of ownership for an indefinite period of time.

In Gangemi v. Zoning Board of Appeals, the Supreme Court of Connecticut found that a condition of zoning variance that prohibited rental of homeowners' property in their beach district was an unreasonable restraint on alienation of homeowners' real property and invalidated it. This is another example of an unreasonable restraint on alienation.