The Deputy Sinn Fein leader, Mary Lou McDonald, says it was inevitable that other responses developed in the absence of a "bona fide" police service in the North.
Ms McDonald was commenting in light of a blog post by Gerry Adams, in which he described the IRA's efforts to fill what he called a "policing vacuum" in the past.
He acknowledged the organisation often punished petty criminals, and shot alleged sex offenders.
He again refuted allegations from Máiria Cahill, but conceded the IRA was "ill equipped" to deal with matters like child abuse and rape.
Deputy McDonald says the IRA's system of justice was born out of a society in crisis, and communities with nowhere left to turn.
She said: "I'm not pretending for a moment that this was a good situation. Let me tell you, the only way to deal with any community justice issue is through agreed democratic structures and through the criminal justice procedure.
"So, I am not advertising this as a good thing that happened, I'm simply saying to you in real terms for people who live through those circumstances, that is what happened and that is the reason."