The IRA are an anti constitutional group and membership is illegal resulting in a prison sentence. During our Civil War in the 20's we had a choice of a legal govt. elected freely by the people under the rule of law or the IRA who saw themselves as the rightful govt.. The main reason they lost was that they didn't have the support of the people.
When I did criminal law during the last term of the law degree we covered a case involving one of these IRA men who was arrested for bank robbery in the 70's. This man shot a member of the Gardaí Siochana (Police) dead in cold blood. This guy refused to acknowledge our law, he also claimed that the elected govt. is illegitimate etc.. Recently they have become Irelands equivalent to the Mafia, before Christmas one of their leaders was assassinated in Dublin by a gang involved in drug dealing and protection rackets, they're considered only criminals who wave the national flag around.
As for the north we have a treaty in place that states that there will be unification only when the people freely wish for it. It is a mature and democratic attitude to have and the IRA's actions only blighted innocent lives.
In my home town we have a little park at the back of the Law Court where they shot six IRA men by firing squad for treason, after independence these men crossed the border into Northern Ireland and planted bombs which killed innocent farmers. One of their colleagues wasn't arrested the amadan blew himself up by accident, he sat on the plunger for the explosives.