Haitians gave notice last week: they have had it with Duvalier-style dictators. This came as news to Roger Lafontant, the former Duvalier security boss who seized the National Palace with a small band of armed toughs, took caretaker President Ertha Pascal-Trouillot captive and declared in cocksure words that all Haiti was behind him. He was proven wrong ill half a day. Responding to the call of conch-shell trumpets, which 200 years ago rallied Haiti’s slaves to revolution, Haitians flooded into the streets of Port-au-Prince carrying posters of President-elect Jean-Bertrand Aristide. Lafontant tried declaring martial law, but troops stormed the palace, arrested him and led him away in handcuff’s. Within minutes Pascal-Trouillot emerged oil a palace balcony and waved to the crowds below.

Exultant Haitians began celebrating what they hoped was the final collapse of the Duvalier regime, which ruled Haiti from 1957 to 1986. But the celebrations quickly turned brutally violent. Enraged by Lafontant’s threats against Aristide, thousands of citizens laid siege to his political headquarters. Crowds hunted down Tontons Macoutes, the security goons commanded by Lafontant under the Duvaliers. By the end of the day, dozens of people were lynched or beaten to death as suspected Macoutes, and their bodies were burned in the streets.

The crowd also searched for Roman Catholic Archbishop Francois Wolff Ligonde, whom many Haitians view as a friend of the Duvaliers and an enemy of Aristide, a radical priest who was expelled from his order in 1988. But Ligonde escaped. As the crowd grew frustrated, vandals burned the capital’s 220-year-old cathedral to the ground, destroyed other church property and chased the Vatican’s diplomatic representative from his office.

The unrest raised fresh doubts about whether Aristide has the power-or the will-to rein in street violence against Duvalierists. Two days after the mob rampage, Aristide condemned the attacks as a “hideous spectacle” and called for “vigilance without vengeance” against alleged Tontons Macoutes, urging Haitians to turn in suspects to the Army. Western diplomats in Port-au-Prince said a stronger and earlier condemnation from Aristide might have stopped the vigilantes. But for Aristide’s constituents - a solid majority of Haiti’s desperately poor population-foreign criticism missed the point: the real worry was whether the old regime would rise again.

For one thing, the Army’s loyalties were still in doubt. In 1987 soldiers stood by and watched as Macoutes hacked voters to death at the polls, effectively canceling the presidential ballot. On Election Day last month the soldiers performed better, keeping order under pressure from hundreds of international observers. In last week’s coup attempt the Army also sided with the forces of democracy, but it had little choice. Had the soldiers not ousted Lafontant and his tiny band, they would have faced a confrontation with thousands of Aristide’s passionate supporters in the streets.

Diplomats praised military commander Gen. Herard Abraham as a hero of democracy. Jean-Claude Roy, president of the Union of Haitian Constitutionalists, said that now “no sensible person can claim that the power in this country is Duvalierist.” But the senior ranks still harbor some Tontons Macoutes, and tens of thousands of other Duvalier thugs also remain free, chastened by the mobs but possibly ready to make trouble again.

Aristide himself has endorsed “the explosion of popular anger” as a last resort to fend off the old regime. Mob justice is precisely what saved his political life last week. The next flash point might come on Feb. 7-Aristide’s Inauguration Day and the fifth anniversary of the fall of the Duvaliers. If Haiti’s democratically elected president manages to assume power as scheduled, his first job will be to take justice out of the hands of thugs and mobs.

Photo: Enraged: A victim of mob violence is torched in the streets of Port-au-Prince