Monday, a judge re-sentenced him to eight years and three months in prison, and ordered him to pay $3.5 million in restitution.
Authorities say more than 130 SUVs were burned or vandalized as part of an environmental protest six years ago. Two other suspects remained at large.
Cottrell's attorney maintains his client helped plot the attacks but didn't take part.
With credit for time served, his attorney says Cottrell could be out of prison in 18 months.
AP contributed to this report.