Russian officials say Georgy Shuppe arranged the January 2014 murder of Alexander Mineev, who was shot 22 times with a Kalashnikov rifle on the outskirts of Moscow.
Shuppe also is accused of fraudulently taking over assets belonging to Mineev. His lawyers say the case is politically motivated.
Shuppe used to be married to the daughter of oligarch Boris Berezovsky, a fierce critic of Russian President Vladimir Putin. Berezovsky was found dead in his English mansion in 2013. An inquest failed to determine whether he was killed or committed suicide.
In a written judgment, Grant said the claims against Shuppe were based on "the account of an anonymous witness who, in turn, reports what he was told by a third party who may or may not have been present when the conversation between two other individuals, not including the defendant, took place." Russia has 14 days to appeal against the decision.
Outside court, 46-year-old Shuppe said he was "pleased and delighted," but couldn't say more.