ITALIAN TERRORISTS have once again kidnapped a public official, this time a judge, and now have threatened to kill him. This ugly affair illustrates the atmosphere of danger in which Italian authorities undertake terrorists cases and the personal courage these prosecutions require. In most countries, judges and prosecutors know there is always some slight chance that a defendant with a grudge may attempt revenge. In Italy, the people who deal with the political cases know they will become targets of radical organizations committed to violence as a deliberate attack on the state.

One of these groups, the Red Brigades, abducted a former premier, Aldo Moro, three years ago and eventually murdered him. Since then the police and the courts have grimly pursued the kidnappers, and currently most -- although not all -- of them are in prison. But another wave of violence began a month ago when the same Red Brigades seized Giovanni d'Urso, a magistrate handling prisoner assignments. The kidnappers began demanding political concessions.

Meanwhile, a few days after Christmas in one of the maximum-security prisons, immates apparently led by convicted terroists rioted and seized hostages. The government responded immediately and successfully. Police commandos, in a skillful assault, broke the rebellion and freed the hostages without serious injury to anyone. Two days later the terrorists replied by assassinating a police official.

In the case of the kidnapped judge, the press has been drawn directly into the debate over concessions. One of the terrorists' demands is publication of political statements by their imprisoned friends. Most of the country's major newspapers have now declared that they will refuse. That's another act of courage. Over the past several years there has been a series of shootings -- some fatal, some deliberately to maim -- of Italian newspaperman by terrorists.

There are now two places in Europe where terrorism is endemic -- Northern Ireland and Italy. The Irish tragedy is rooted in a well-known history. The Italian case is harder to explain. Perhaps part of it is the social strain of very rapid development. Perhaps a larger part is the stunted political tradition that has left one faction-ridden party in control of the government continuously since 1948. But if the origins are obscure, the cost is very clear. In countries where the disease of terrorism takes hold, even the most ordinary processes of law enforcement and justice require extraordinary bravery.