MEXICO CITY, Mexico — After carefully packing light green Mexican marijuana into a homemade water pipe, university student Salvador Chavez drew a deep breath from the tube and blew the smoke out of the window of his modest family home.

“I don’t care if the neighbors call the police on me. They can’t arrest me for this anymore,” he said behind lightly glazed eyes. “But then police here never cared much about a bit of marijuana anyway. Everything has just stayed the same really.”

Almost two months after Mexico decriminalized the possession of small amounts all major narcotics — including marijuana, cocaine and heroin — the most notable thing is how little has changed.

Drug users and addicts still smoke, snort and inject quietly in their homes; drug dealers are still regularly arrested in stash houses and on street corners; and major cartels carry on battling police to smuggle huge loads to the United States.

But while the law has yet to have a measurable impact on the Mexican streets, it has sent waves across the Americas to groups campaigning to change drug laws in their own countries.

Shortly after Mexico enacted its decriminalization act on Aug. 20, the Supreme Court of Argentina ruled that it was unconstitutional to punish people for personal consumption of marijuana.

“The state cannot establish morality,” Argentine Supreme Court President Ricardo Lorenzetti said following that ruling.

The Argentine Congress is now looking to change its laws accordingly.

Then weeks later in Colombia, the Supreme Court also ruled that people could not be prosecuted for possession of narcotics for personal use, resisting pressure from conservative President Alvaro Uribe to lock up drug users.

“Real change is happening. More and more people over the world are taking a more rational view on drugs,” said Maria Lucia Karam, a retired judge in Brazil who is part of the pro-legalization group Law Enforcement Against Prohibition.

“People are understanding that the prohibition of drugs does more damage than the actual drugs themselves,” she said.

A similar court ruling to that of Colombia and Argentina may soon be passed in Brazil, Karam said.

Latin American legalization advocates have been particularly encouraged by the muted United States reaction to the Mexican law.

For decades, the U.S. government pushed hard to pressure Western hemisphere nations to take a hard line on drugs, blocking certain aid programs if it ruled that anti-narcotic efforts were not sufficient.

Furthermore, in 2006 the White House condemned a previous attempt by Mexican lawmakers to decriminalize drugs, leading then-President Vicente Fox to refuse to sign the bill.

However, following Mexico’s new law, the Obama administration has been virtually silent on the issue.

Asked about the upcoming changes in a visit to Mexico in July, Drug Czar Gil Kerlikowske said he would “wait-and-see.” Two months after the law has been enacted he still seems to be waiting and seeing.

“The current administration seems to be taking a much more pragmatic approach to the issue,” said Joe Rogoway, a spokesman for the California Cannabis Initiative, which campaigns for the legalization of marijuana.

Rogoway said the ease with which the Mexican law slipped in has also encouraged anti-prohibition groups north of the Rio Grande.

“It is a positive start in the right direction,” he said. “It is all about harm reduction. And not throwing a drug user in jail definitely helps alleviate any harm to them.”

The group is gaining signatures to put a motion to completely legalize marijuana in California on the ballot in 2010. Under current California law, marijuana is legal for medical use while possession for personal use can be punished with a fine.

However, some groups see the Mexican law and its ripple effects as a step backward rather than forward.

“Decriminalization is clearly a victory for the drug sellers,” said Calvina Fay, the executive director of the Drug Free America Foundation. “When people are taking drugs they are not innocent victims. They are impacting many lives and they need to be held accountable.”

Fay argues that rather than taking a softer approach, the United States and its Latin American allies should take a harder line on drugs — including more crop spraying and drug testing in schools and work places.

“The mantra that the war on drugs doesn’t work is a big fat lie,” Fay said. “We have made real progress since the 1970s in fighting back drug use. It is crazy to surrender now.”