Power, in law, an authority by which one is enabled to exercise the control of an owner over the property of another. The term is important in real estate law, where powers are variously classified with reference to their origin and incidents. They may be created by deed, will, or other instrument executed by the owner of the land, as where one by will empowers his executor to sell or mortgage lands for the purpose of raising portions for children, or by letter of attorney constitutes another his agent to make sales; or they may result from legal proceedings, or be conferred upon officials by statute for the purpose of enforcing some public right or private remedy. A common instance of a statutory power is the authority to make sale of lands for the nonpayment of taxes. Powers also are " naked," or disconnected from any interest in the land, or they are coupled with an interest, by which is meant that the donee of the power has an interest not in the execution of the power merely, but in the property in respect to which the power is created. Thus an attorney to sell lands has a naked power, though he may be benefited by its execution; but a mortgagee in a mortgage which contains a power of sale has a power coupled with an interest.

The distinction is important, as in general the donor of a naked power may revoke it at any time, and his death (except where it is given by will) or his bankruptcy will revoke it. Powers are again classified as those which have effect under common law rules, and those deriving their force from the statute of uses. A power of the latter class is an authority to cause a use with its accompanying estate to spring up or shift from one person to another at the will of the person invested with it. These are sometimes made use of in family settlements, as a means of providing for events and contingencies which cannot be fully foreseen, and they may or may not indicate the beneficiary. If they do not, the donee may designate whomsoever he shall please, or abstain altogether; but if they do, they are powers in trust, and equity may compel the execution. A power is to be executed as provided by the instrument creating it, if provision be made therein; and a common law power not coupled with an interest is to be executed in the name of the donor of the power, except when given by will.