"Sadretdinov was arrested on specious grounds," said Sadretdinov's lawyer, Ruslan Koblev.
Another lawyer, Ruslan Zakalyuzhny, said Sadretdinov had been arrested in his notary's office without any explanations.
Sadretdinov and two other defendants, Kazbek Dukuzov and Musa Vakhayev, were acquitted by majority jury verdict May 5 at Moscow City court.
Prosecutors in the case claimed Dukuzov, Vakhayev and Sadretdinov gunned down Klebnikov on July 9, 2004, on the orders of Chechen businessman Khozh-Akhmed Nukhayev, who wanted revenge after Khlebnikov's critical book "Conversations with a Barbarian" featured him as the central figure.
Klebnikov, a United States national, had worked for Forbes since 1989 and gained his reputation for investigating murky post-Soviet business dealings and corruption.
According to the prosecution, Nukhayev recruited a Chechen gang, including Vakhayev and Dukuzov - arrested by Belarusian police in Minsk on November 17 last year - and two other men, named as Magomed Dukuzov and Magomed Edilsultanov. They remain on the federal wanted list.