The attackers are essentially gang members enforcing their own version of justice in communities where law enforcement is either unwelcome or fears to intervene. Sometimes they claim to be policing “anti-social behavior” such as drug dealing, but Harbinson says the perpetrators are often dealing drugs or participating in other criminal enterprises themselves and trying to protect their turf.

Unlike the violence that defined the Troubles, when members of different religious communities attacked each other in a struggle over British control of Northern Ireland, in these cases the assailants target their own.

“It’s not sectarian at all. What this is, is Catholic on Catholic, Protestant on Protestant,” Harbinson said. “It’s about control within their own communities.”

Northern Ireland’s struggle with paramilitaries illustrates just how complicated it is to end a war, even in the event of a successful peace deal. For many conflicts around the world, the Good Friday Agreement represents the best-case scenario of power-sharing and disarmament. But Northern Ireland’s continuing violence also shows how the societal distortions and the trauma of a long-ended conflict can continue to tear at communities, leaving them in a condition that’s not technically war but is far short of real peace.

Read: The Good Friday Agreement in the age of Brexit

The attacks take the form of shootings in the ankles, elbows, or knees (“sometimes all six,” Harbinson says), or beatings with hammers or clubs. The objective is not generally to kill, though some result in fatalities. Frequently, the victims know their attackers personally, since they all hail from the same close-knit communities. And often, as the new PSA depicts, the victims themselves show up, or their parents take them, to an appointment to be beaten or shot—they fear worse if they don’t.

Northern Ireland police say so-called punishment attacks like this are markedly higher than five years ago. But the origins lie in the deeper dynamics of the conflict, which didn’t so much end as shift into another domain.

The violence of the Troubles took some 3,600 lives over a 30-year period. When the Good Friday Agreement laid out provisions for a unity government and the disarmament of paramilitaries in 1998, sectarian violence across the country swiftly plummeted. Even then, though, there was evidence of a key problem left unsolved.

“It is a funny sort of peace in which people are regularly maimed and driven from their homes by paramilitary thugs,” wrote The Economist in 1999, a year after the agreement was signed. The punishment attacks weren’t mentioned in the accords; they weren’t, after all, the kind of Catholic-on-Protestant violence that the peace deal was meant to stop.

But the phenomenon had developed alongside the Troubles, for different reasons in different communities, explains Rachel Monaghan, a senior lecturer in criminology at the University of Ulster who has researched intra-communal violence in Northern Ireland. In the case of Catholic republican communities, who sought independence from British control, paramilitaries formed in opposition to—or defense from—the police. In Protestant loyalist areas, they formed as a kind of auxiliary to the authorities.