In contract law, the need for ratification can arise in two ways: if the agent attempts to bind the principal despite lacking the authority to do so; and if the principal authorizes the agent to make an agreement, but reserves the right to approve it. An example of the former situation is an employee not normally responsible for procuring supplies contracting to do so on the employer's behalf. The employer's choice on discovering the contract is to ratify it or to repudiate it.
The latter situation is common in trade union collective bargaining agreements. The union authorizes one or more people to negotiate and sign an agreement with management. A collective bargaining agreement can not become legally binding until the union members ratify the agreement. If they do not approve it, the agreement is void, and negotiations resume.