Did they have to completely relearn law or get re-certified? We're they completely replaced and put out of work? What was a indicative experience for a lawyer through the revolution and afterwards?
As a chess historian, I can tell you about the experience of Alexander Alekhine (4th World Champion). Alekhine finished his law degree in St. Petersburg in 1916. He then served near the front lines of WWI as a medic, earning several decorations. However, as a member of the former nobility (his father, a member of the Duma, was executed during the Revolution), Alekhine was scrutinized. He was imprisoned in Odessa in 1919 under suspicion of being a "White Russian", and was very nearly executed until a clerk (who also happened to play chess) called the head of the secret police to intervene.
Alekhine then returned to Moscow where he worked for a time as a prosecutor (without having to re-learn or re-certify), then worked as a translator in The Communist International (Comintern). He then married a foreigner and defected to France, never practicing law again.
Most of this information comes from:
Kotov, A., and Alexander Alekhine. Alexander Alekhine. London: B. T. Batsford, 1975. Print.
However, Kotov (a Russian Grandmaster) conveniently neglects to mention that Alekhine's father was executed and that Alekhine nearly faced the same fate.