seven explained it all, just a tiny remark: fifa allows clubs to terminate contracts with just cause. this is it, this is just cause. btw it has been already confirmed by journos that in case of a ban, not only we have the right to, but we'll also terminate the contract.
pogba can of course follow his own legal path and sue the antidoping agency that will ban him. if he wins, then he'll have a right for a compensation. not from juve though, that would be on the agency. at least that's what i've gathered from the articles on the palomino case (which is btw completely different, palomino's sample was contaminated, which isn't the case with pogba, he allegedly admitted the use of the banned substance, end of the story)