Koblyakov, a joint French and Russian citizen, is one of the leaders of "Russia-Freedom", a group which has organised several protests against Putin in France.
It has also published reports on corruption among the Russian elite.
Moscow demanded his extradition, accusing him of falsifying signatures on documents in 2004.
But a Paris court ruled that any infringements by Koblyakov were only committed in France.
"This decision gives me courage to continue to fight for the promotion of freedom in Russia," Koblyakov told AFP.
In July 2014, Koblyakov was arrested in Bulgaria on an Interpol arrest warrant requested by Russia.
The Bulgarian authorities refused his extradition, saying insufficient information had been presented by Russia.