MOSCOW >> The authorities have dismissed software piracy charges against one of Russia’s best-known environmental groups after Microsoft indicated that it would no longer support the case.

The police in the Siberian city of Irkutsk raided the offices of the group, Baikal Environmental Wave, in January and confiscated 12 computers, all but paralyzing its operations. Investigators said they believed that Baikal Wave had unlicensed Microsoft software on its computers, but the environmentalists said the motivation for the raid was political.

The authorities dropped the charges after The New York Times published an extensive account of the case Sept. 12 that prompted Microsoft to overhaul its policies in Russia.

The article described how in Irkutsk and across the country, prosecutors and the police had regularly used the pretext of software piracy investigations to undermine advocacy groups and opposition media outlets.

Private lawyers retained by Microsoft had often assisted in these investigations, referring to the company as a victim and asking that criminal charges be brought. The company had rebuffed appeals from those being investigated, saying that it was only following the law.

Baikal Wave did not learn that the software piracy case had been closed until recently. After repeatedly asking the Irkutsk police for information, the group said it received a terse letter from police officials explaining that they had ended the inquiry on Sept. 22 because of the “absence of a criminal act.”

Baikal Wave had from the start maintained that all its software was legal, but the police had continued to pursue the case, and for months, the group had faced the prospect of criminal sanctions, including possible jail time for its leaders.

It appears that the authorities could not move forward in part because Microsoft would no longer help them.

The day after the article was published in The Times, Microsoft apologized for its role in these cases and said it would no longer have any involvement in them. The decision would seem to have made it very difficult for the authorities to deploy what had been an increasingly common law-enforcement tactic against government critics.

Microsoft also contacted police officials in Irkutsk and urged them to drop the Baikal Wave case, according to Marina Levina, a spokeswoman for Microsoft in Moscow.

“With the benefit of hindsight, we realize we perhaps could have done more” to help Baikal Wave, Levina said.

Galina Kulebyakina, a co-chairwoman of Baikal Wave, said Microsoft’s turnabout had damaged the credibility of the Irkutsk police’s case. “They had no choice but to dismiss the charges,” Kulebyakina said.

She said the authorities had not formally announced their decision because they were embarrassed at how the case had turned out.

Baikal Wave has long contended that the police carried out the raid to prevent the group from organizing a demonstration against a decision by Prime Minister Vladimir V. Putin to reopen a paper factory that has polluted nearby Lake Baikal for decades. The lake by some estimates holds 20 percent of the world’s fresh water.

The police in Irkutsk did not respond to requests for comment. In earlier statements, police officials had said that the Baikal Wave inquiry had nothing to do with the group’s activities.

In addition to changing its policies in Russia, Microsoft announced a major plan to help the nonprofit sector and to prevent political crackdowns from being carried out by the authorities under the guise of software piracy inquiries.

The company said it would provide free automatic software licenses to more than 500,000 advocacy groups, independent media outlets and other nonprofit organizations in 12 countries with tightly controlled governments, including Russia and China.

Last month, Microsoft flew several leaders of Russian nonprofit groups, including Kulebyakina, to New York City for consultations on the free software licenses. The meeting was organized in part by Human Rights First, a U.S. group that has worked closely with Russian advocacy groups, including those subjected to software piracy investigations.