Rule 21 of the Gaelic Athletic Association (GAA) was a rule in force from 1897 to 2001 which banned members of the British security forces from membership of the GAA and thus from playing Gaelic games. The affected organisations included the British Armed Forces and the Royal Ulster Constabulary (RUC), and prior to partition, the Royal Irish Constabulary (RIC) and Dublin Metropolitan Police. As well as the RUC in Northern Ireland, it also applied to police forces in Great Britain, which affected London GAA and the other British GAA affiliates. Rule 21 stated: Members of the British armed forces or police shall not be eligible for membership of the Association. A member of the Association participating in dances, or similar entertainment, promoted by or under the patronage of such bodies, shall incur suspension of at least three months. The rule was abolished after the establishment of the Police Service of Northern Ireland (PSNI) as part of the Northern Ireland peace process. Origin Rule 21 was introduced in 1897 and reflected the rise of "advanced nationalism", with the GAA and other Irish nationalist organisations founded in the Gaelic revival becoming more politicised and separatist in the build-up to the revolutionary period. It was intended to allay fears that RIC members were joining GAA clubs to spy on members' political activities. It was overshadowed by the introduction in 1901 of Rule 27, commonly called "The Ban", which prohibited GAA members from playing "foreign games" like soccer and rugby union. In 1938 Douglas Hyde, recently inaugurated as first President of Ireland, was removed as Patron of the GAA after attending an Irish soccer international. After Rule 27 was abolished in 1971, it was Rule 21 and Rule 42, which prohibited foreign games being played at GAA grounds, which were the focus of debate. Northern Ireland After the 1922 creation of the Irish Free State, Rule 21 continued to apply in Northern Ireland. Its strongest supporters were physical force republicans, and during the Troubles the GAA was suspected by many unionists of collusion with the Provisional IRA and other paramilitaries. While some advocates of Rule 21 were opposed to any engagement with "Crown forces", others linked it to alleged targeting by the security forces of the GAA, in particular the occupation of part of Crossmaglen Rangers' grounds by a British Army base, which disrupted matches and other events there. One player affected by the