Given the series makes a point of the difference between the FBI and CIA's operating remit, it's surprising that in this episode they either manage to confuse MI5 with MI6, or Northern Ireland with the Republic of Ireland.
MI5 only has authority within the UK, whereas MI6 is the foreign intelligence service. The assassin Maya was supposedly MI5, but when she disappeared was working an operation on a cell out of Dublin and killed in Kerry, both of which are in the Republic of Ireland. The RoI is an independent country quite separate from the UK so either she was in the wrong service or she was in the wrong country.
MI5 only has authority within the UK, whereas MI6 is the foreign intelligence service. The assassin Maya was supposedly MI5, but when she disappeared was working an operation on a cell out of Dublin and killed in Kerry, both of which are in the Republic of Ireland. The RoI is an independent country quite separate from the UK so either she was in the wrong service or she was in the wrong country.
Quinn accuses Devlin of "crimes against the Irish people", which is odd because as an MI5 agent she'd consider Northern Ireland and its citizens to be British not Irish. The goal of the IRA was for Northern Ireland to secede from the UK and become part of the Republic of Ireland, so they'd be exceedingly unlikely to launch a terrorist attack in the Republic they were notionally fighting for.