A YEAR AGO terrorists bombed Omagh in the British province of Northern Ireland, killing 29 persons and injuring 350. In the shock, people of almost all political stripes recommitted themselves to peace. A year later, however, the Good Friday peace agreement teeters on the verge of irrelevance, and in Omagh itself, The Post's T. R. Reid reports, a terrible trick has been played on hope.

It seems that everyone, including the authorities, knows exactly which individuals -- people linked to the Irish Republican Army splinter that has claimed credit for the bombing -- committed this atrocity. Still, the police have been unable to keep anyone in jail or to bring anyone to trial. Either likely witnesses have been intimidated by IRA threats of beating and killing, or they simply refuse to cooperate, for political reasons, with the British-run constabulary in Northern Ireland. Says Martin McGuinness of Sinn Fein, the IRA's political arm: "I am not an informer. You can't ask me to confer legitimacy on the policing power. I have no respect for the [constabulary]. I won't help them."

It seems no big problem to Mr. McGuinness and his colleagues that in order to "deny legitimacy" to the existing police he is condoning mass murder. His statement has the effect of giving a free pass to political crimes until the administration of justice has been reformed according to the terms of the Good Friday agreement. But of course the Omagh bombing is one of the principal events stymieing the fulfillment of Good Friday. In its ideological rigidity, Sinn Fein is delivering crucial political power to an unreconstructed splinter faction of the IRA, a splinter that Sinn Fein ostensibly repudiates.

Sinn Fein is toying with the future of its country. The right way for it to demonstrate its readiness for conciliation and peace is to allow the wheels of justice to turn in the Omagh tragedy.