BOGOTÁ, Colombia, June 22 - Colombia's Congress on Wednesday approved a law governing the disarmament of the country's death squads, which permits the demobilization of thousands of fighters but grants generous concessions to paramilitary commanders accused of atrocities and cocaine trafficking.
The Justice and Peace Law, an underpinning of President Álvaro Uribe's goal of pacifying Colombia, was hailed by government officials as a way to lay the groundwork for removing one of the three illegal armed groups battling in Colombia. "We are proud of this instrument," said Luis Carlos Restrepo, the country's peace commissioner.
But congressional leaders say that in exchange for disarming up to 20,000 fighters, paramilitary commanders are shielded from serious punishment or extradition on drug charges to the United States. The law, passed by Congress on Tuesday and by bicameral committees on Wednesday, will be signed into law by Mr. Uribe within days.
"This is a law that brings no justice, no peace," said Senator Jimmy Chamorro. "It should be called what it really is, a law of impunity and immunity."
Washington has listed 18 paramilitary commanders as among Colombia's top cocaine kingpins, and American counternarcotics officials say the paramilitary group, the United Self-Defense Forces, is responsible for trafficking most of the cocaine reaching American cities. The group, founded by landowners and drug traffickers to battle Marxist rebels, is also blacklisted by the State Department as a terrorist organization accused of assassinating politicians and killing thousands of peasants.
"This gives benefits to people who have committed the worst crimes, and we get nothing in return," said Gina Parody, a leading congresswoman and ally of Mr. Uribe who nevertheless proposed much tougher legislation. "The message we are sending to Colombian society is that crime does pay."
The law highlights the contradictory nature of United States policy in Colombia, which has received more than $3 billion in mostly military aid since 2000 to destroy drug crops and weaken guerrillas.
The law shields the paramilitary commanders from extradition on drug charges by allowing them to confess to trafficking, giving them double-jeopardy protection. It also categorizes "paramilitarism" and related crimes as political crimes, which under the Constitution would safeguard the commanders from extradition on the related crime of trafficking.
The Bush administration and its representative in Colombia, Ambassador William Wood, have strongly supported the law and Mr. Uribe, who has made disarming the paramilitaries a cornerstone in his campaign to win re-election.
But some influential members of the United States Congress have raised dire warnings.
"We want to see the armed groups demobilize, but this law rewards some of Colombia's worst terrorists and drug traffickers without any assurance that their criminal organizations will be dismantled," said Senator Patrick J. Leahy, a Vermont Democrat who is the ranking member on the foreign operations subcommittee and works on Colombia policy.
In a letter to Mr. Uribe last month, Senator Richard G. Lugar, the Republican who is chairman of the Foreign Relations Committee, said he was concerned that the law "would leave intact the complex mafia-like structures" by failing to require commanders to disclose knowledge of the organization's operations or financing.
The law contrasts sharply with how other South American nations are now dealing with rights violators in the aftermath of civil conflicts.
In Argentina, the Supreme Court last week ruled that 19-year-old laws granting amnesty to military officers who committed atrocities during that country's so-called dirty war are unconstitutional. In Chile, hundreds of former military officers have been charged with crimes committed during Gen. Augusto Pinochet's rule.
Here, the United Nations high commissioner for human rights in Colombia, Michael Frühling, as well as human rights groups and members of Colombia's Congress, said Mr. Uribe had settled on disarmament at too high a price after a year of official negotiations in a 142-square-mile safe haven where paramilitary commanders operated freely. Critics say the law would do little to compensate victims, recoup land under paramilitary control or disclose the truth about atrocities.
"If you do not clear up what happened and reveal the illegal structures that exist, you not only do not have justice or offer reparations for victims, but you also do not have the elements to dismantle these illegal structures," Mr. Frühling said.
The biggest concern in Washington is that commanders who are, in essence, drug traffickers will remain largely free to continue moving cocaine. The United States has issued extradition orders on at least six commanders, including the most powerful leader, Diego Fernando Murillo, a former underworld hit man wanted by federal prosecutors in New York.
"They are very much involved in drug trafficking activities," an American counternarcotics official said. "If you ask me whether we have heard of a reduction of drug trafficking by those very people who were sitting at the negotiating table, I would say, 'No.' "
The government says that with the negotiations, hundreds of lives have been saved as more than 5,200 paramilitaries have disarmed since late 2003.
But under the law, commanders do not have to guarantee that all their fighters will disarm, or that those fighters adhere to a cease-fire. Critics also say the law does not require a complete and honest confession from commanders in return for sentencing-reduction benefits.
Commanders can, in theory, be charged with crimes, but investigations are restricted and punishment is light - as little as 22 months and possibly on farms, not in prisons.
"This law tries to simulate truth, justice and reparations, but what it really offers is impunity," said Iván Cepeda, whose father, Senator Manuel Cepeda, was killed by paramilitary gunmen in 1994.
Victims' families outraged by the law included Leonel Sánchez, whose son, Jairo Hernando Sánchez, 29, was kidnapped and killed by paramilitaries in 2003.
"It is grave that this law protects them from war crimes, crimes where so many poor people died," said Mr. Sánchez, 57.