The European Court of Human Rights has ruled that Russia illegally detained international chess star and opposition leader Garry Kasparov in 2007.

In May of that year, Kasparov was trying to fly from Moscow to Samara, in western Russia, to attend a march against the administration of Russian President Vladimir Putin, planned to coincide with a summit between Russia and the European Union. At 8:30 a.m. at Moscow's Sheremetyevo airport, authorities confiscated his ticket and passport, and then held him for five hours.

He missed the flight, and the protest march.

Kasparov first filed a complaint in a Russian court, saying his right to free assembly had been infringed upon. The Russian government insisted the police were conducting "a wider investigation into ticket forgery," according to the European court's decision.

The initial complaint was dismissed by the Golovinskiy District Court of Moscow in 2007. An appeal in Russia was also dismissed, at which point he took the case to the European Court of Human Rights, which is composed of seven judges, one of whom is Russian.

The seven judges unanimously agreed that Kasparov had been illegally detained, and that it amounted to "interference with his right to freedom of assembly," noting the Russian government had not provided any evidence to support the ticket forgery investigation claim.

Kasparov has devoted his time to Russian opposition politics since he retired from international chess competition in 2005. He was the highest-ranked chess player in the world from 1985 to 2005.

Since then, he has frequently and publicly criticized Putin. After the Russian president's party swept 70 percent of the seats in a 2007 election, Kasparov accused the authorities of not only "rigging, but also raping the democratic system." He was arrested with the opposition punk group Pussy Riot in 2012.

Earlier this year, he told Reuters, "Confrontation with Putin is inevitable as long as he stays in office." He even wrote a book, the subtitle of which is "Why Vladimir Putin and the enemies of the free world must be stopped."

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