A central figure in the spreading search for West German terrorists and their alleged supporters was arrested in Paris today.

West German lawyer Klaus Croissant, 48, defender for the Baader-Meinhof terrorist gang, is wanted in West Germany on charges of supporting terrorist groups. He fled illegally to France last July.

Shorty after Croissant's arrest was announced, West German prosecutors also said they had formally brought charges of complicity in murder and seizing of hostages against another former Baader-Meinhof lawyer, Siegfried Haag.

Haag, 32, is charged with helping to plan and provide weapons for the 1975 terrorist attack on the West German embassy in Stockholm in which two diplomats were killed. Haag has been in West German jail since his arrest last November.

Perhaps coincidentally, both developments come within hours after the West German Parliament approved an extraordinary new law that permits the isolation of jailed terrorists from each other and from their lawyers for temporary periods during times of emergency. The new law, which takes effect Sunday, comes in the aftermath of a string of terrorist attacks in the past five months that have stunned West Germany.

Croissant was removed by the court from the Baader-Meinhof defense team just before the trial of the urban guerrilla group began in May 1975. He was under suspicion of supporting the terrorists' aims.

Since then, he has become the most prominent member and perhaps the intellectual leader of a group of a dozen or so radical lawyers who operated out of his Stuttgart offices.

Croissant was subsequently charged but released on bail and warned not to leave the country. He fled to France seeking asylum.

In the aftermath of the kidnaping of industrialist Hanns-Martin Schleyer on Sept. 5, a state-owned French television station carried an interview with Croissant at a time when the French police were supposed to be unable to find him.

Croissant said the struggle of the "Red Army Faction," left-wing extremist group in West Germany, was a fight "against a regime that has already entered into a disguised fascism."

The interview and subsequent anti-German articles in the French press outraged Bonn and brought a personal apology from French President Valery Giscard d'Estaing.