A right given to a person to be the first person allowed to purchase a certain object if it is ever offered for sale. The owner of this right is the first to be offered the designated object if it is ever to be offered for sale. The extent of these rights varies from country to country and may include the right to build a wharf outwards to a navigable depth or to take emergency measures to prevent flooding. A common law rule that prevents suspending the transfer of property for more then 21 years or a lifetime plus 21 years. For example, if a will proposes the transfer of an estate to some future date, which is uncertain, for either more than 21 years after the death of the testator or for the life of a person identified in the will and 21 years, the transfer is void.
Statute law exists in many jurisdictions which supersedes the common law rule.