His legal troubles began when he used his wealth and influence to support the liberal political forces in Russia. Putin warned him to back off from politics, but Khodorkovsky ignored the warning. So, in 2003, the Kremlin arrested his partner, Platon Lebedev. Still, Khodorkovsky continued to dabble in politics. The Kremlin responded by arresting Khodorkovsky himself, and a Russian court then sentenced him to 8 years in prison. Before today's court ruling against him, he would have been released from prison in 2011. Today's ruling means that he will likely stay in prison until 2017.
The report just published by the BBC offers another view of this matter.