The Moscow Region Court issued a ruling based on the jury's not guilty verdict of June 5. Colonel Vladimir Kvachkov, a former General Staff member, and two former paratroopers Alexander Naidenov and Robert Yashin were released from custody following the reading of the verdict.
The assassination attempt occurred close to Moscow on March 17, 2005 when a bomb exploded as Chubais' car was passing and his vehicle subsequently came under attack from men armed with automatic weapons. Chubais was not hurt in the attack.
According to prosecutors, the defendants were motivated by their extremist views and a violent dislike of Chubais, an architect of economic reforms in the 1990s that impoverished millions and handed vast fortunes to a handful of well-connected oligarchs.
On June 6, the Moscow City Court extended custody for a fourth suspect in the case, Ivan Mironov. The court upheld an appeal by the prosecutor's office for Mironov to be remanded in custody for a further three months until September 11.
The Moscow Region Court also ruled Monday that the case files be returned to the Investigation Committee under the Russian Prosecutor General's office.
The former defendants' lawyers said prosecutors planned to appeal the court ruling.
Kvachkov, allegedly a key figure in the assassination attempt, said earlier the acquittal verdict was "an act of civic courage."
Chubais has said he was unhappy with the verdict. "I consider it a mistake," he said.
Chubais is currently behind a series of unpopular decisions to raise electricity tariffs.
