Primary responsibility for law and order, including the protection of the internal security of the State, rests with An Garda Síochána. Among the roles assigned to the Defence Forces is the provision of Aid to the Civil Power (ATCP) which, in practice, means to assist An Garda Síochána when requested to do so.
On occasions, the Defence Forces are deployed to Shannon Airport in an ATCP role in support of An Garda Síochána. When deployed in such a role, Defence Force personnel operate in accordance with standard procedures governing the use of force and remain under the operational command of a Defence Forces Officer who has discretion in relation to the degree of force, if any, that is to be used in particular circumstances.