Absolutely it is. There is two centuries of precedence marking copyrighted works as property. It's literally called intellectual property. The courts have only made clarification that intellectual property doesn't violate physical property theft laws (denying ownership), but instead intellectual property theft laws (denying compensation).
But "possession of stolen property" is a specific criminal charge that doesn't typically have to do with copyright (being more to do with, say, bicycles). I can't find any example of "possession of stolen property" charges being brought against a copyright violator, but it's a hard thing to Google.