Revenue stamps of the United Kingdom
When Ireland was partitioned into Northern Ireland and Southern Ireland in 1921, separate revenue stamps were issued for both entities. Southern Ireland stamps saw little use since that political entity was quickly superseded by the Provisional Government of Ireland and later the Irish Free State (both of which applied overprints on various British and Irish revenue stamps). However, Northern Ireland continued to use separate revenue stamps until the 1980s. Northern Irish revenues include Civil Service, Dog Licence, Excise and National Insurance stamps, among many others.
Irish in the British Armed Forces
After the secession of most of Ireland as the Irish Free State and the partition of Ireland, which led to the creation of Northern Ireland, the rule continued to be in place. Particularly during The Troubles, there was a climate of mutual suspicion, as some Ulster unionists regarded elements of the GAA as sympathetic in some ways to the goals of the Provisional IRA and at the same time, the GAA (especially in the North) were suspicious of Royal Ulster Constabulary personnel wishing to join. As part of the Northern Ireland peace process and the reforming of the police into a more cross-community institution, as the Police Service of Northern Ireland, moves were made to lift the ban. In 2001, during the presidency of Seán McCague, the ban was lifted, with 26 counties voting yes. Members of the Irish diaspora serving in the Irish Guards founded the "Gardaí Éireannach" as part of the London GAA in 2015.