In a scathing indictment of the Russian criminal justice system on Thursday, Judge Timothy Workman said he was satisfied Ahmad Zakayev could easily face torture for his political opinions.
London's Bow Street Magistrates' Court also dismissed Russian evidence that sought to link Zakayev to various crimes, including murder.
"I am satisfied that the motivation of the government of the Russian Federation was and is to exclude Mr Zakayev from continuing to take part in the peace process and to discredit him as a moderate," he concluded.
Russia had accused the Chechen envoy of 13 crimes - including murder, kidnapping and soliciting others to murder during the war in the breakaway republic.
After emerging victorious, Zakayev, who has been in Britain since late last year, said he "unconditionally" viewed the ruling as a political victory.
"I will continue to seek peace for the Chechen people," he told journalists.
Russian forces drove most of Chechnya's independence fighters into the mountains in the first few months of the latest conflict after President Vladimir Putin ordered his troops back into the region, following their defeat in 1987.
“I was unable to accept the view... that the actions of the Russian government in bombing Grozny were counter-terrorist operations"
But they have failed to restore peace and still fall prey to frequent resistance attacks.
Moscow has not issued casualty figures for its forces in Chechnya since last December, when it said more than 4500 had died since hostilities resumed in late 1999.
The judge on Thursday said the Russians had argued that the events in Chechnya were not a war and therefore killing their soldiers was murder.
But he added: "I have taken into account the scale of the fighting, the intense carpet-bombing of [the capital] Grozny with in excess of 100,000 casualties
“I was unable to accept the view expressed by one witness that the actions of the Russian government in bombing Grozny were counter-terrorist operations."
Workman also quoted one witness as saying "Chechens are almost always tortured" and said he believed the evidence of another witness who testified that he had been held in a pit for six days and tortured with electric shocks to force him to make a statement against Zakayev.
That witness's evidence was "clear, unequivocal and unshaken by cross-examination," the judge concluded.