To do this, the parties would have to sign a contract under which they would cooperate to achieve a common goal. Their rights and obligations under the agreement would be set out in the treaty. If land is sold at least for its total market value, it is unlikely to be State aid. However, where a local authority intends to sell land for less than market value, it must consider whether there are State aid problems and, if so, how to remedy them. A local authority must ensure that any measure it takes falls within its competence, otherwise it is illegal. When entering into a transaction, a local authority must determine the appropriate authority and ensure that it acts appropriately in the exercise of power. The aim is to ensure that the local authority is able to avoid any challenge to its actions or, if it presents challenges, to successfully defend any challenge. The House of Lords introduced an amendment to the Data Protection Act under which an authority or body is only a public authority or body when it carries out a task in the public interest or in the exercise of official authority entrusted to it. .