"The court ruling has been announced, and it is positive for my client. However, the size of the compensation and the exact text of the ruling have not been announced - this will be published in mid-July," Mikhail Yoffe said.
Kononov, 84, who led a group of partisans in the Baltic state during WWII, was convicted by Latvian authorities of ordering the killing of nine villagers in 1944, with some reports saying the dead included a pregnant woman.
Kononov admitted the killings, but said the dead were Nazi collaborators, and had been caught in cross-fire. The republic was under Nazi occupation at the time of the incident.
Kononov demanded 5 million euro ($7.8 million) compensation for being held in custody in 2002.
A retired police colonel born in Latvia, Kononov was arrested in 1998 and sentenced to six years in prison in 2000 on genocide charges. In 2004, after several years of litigation, his sentence was cut to 20 months in prison and the charges changed to "war crimes." Kononov filed an appeal with the court in Strasbourg the same year.
Russia subsequently brought pressure to bear on Latvian and European authorities over the case, and in April 2004, Russian President Vladimir Putin granted Kononov Russian citizenship.
In 2007, the European court dropped all charges against Kononov, and ruled he was not guilty.
"This is my final victory, one I have been seeking for eight long years," he said then.
While Russia maintains that the Red Army liberated the Baltic states of Latvia, Lithuania and Estonia from Nazi invaders, many local residents fail to distinguish between the Nazi and later Soviet periods.
The European court said on Thursday it would announce its ruling on the Kononov case on July 24.
