Agency law is concerned with any "principal"-"agent" relationship; a relationship in which one person has legal authority to act for another. The relationships generally associated with agency law include guardian-ward, executor or administrator-decedent, and employer-employee. Agency is an agreement, express , or implied, by which one of the parties, called the principal, entrusts to the other, called the agent, the management of some business; to be transacted in his name, or on his account, and by which the agent assumes to do the business and to render an account of it. As a general rule, whatever a man may do by himself, except by virtue of a delegated authority, he may do by an agent.
When the agency is express, it is created either by deed, or in writing not by deed, or verbally without writing. When the agency is not express, it may be inferred from the relation of the parties and the nature of the employment without any proof of any express appointment.
The agency must be given ahead of time, or subsequently adopted; and in the latter case there must be an act of recognition, or an acquiescence in the act of the agent, from which a recognition may be fairly implied.