Okay, so pretty much an act is just a guideline for people to follow. Something that says "Companies can sue if ____" not like a law that the government enforces.
Anyway, ignore that.
Pretty much a company could only win if they somehow got a third party to go through the person's computer and found a copy, or keep track of if he downloaded it from the site after selling it (if attached to his account).
Seems kinda unlikely that they'd ever get the evidence in the first case (doubt a judge would demand the guy hand over his stuff if there is no reasonable cause that he still had copies, if they even do that in civil cases), leaving the second option as the only reliable one.
So they'd have to know when he sold it and then make sure he doesn't download it. But if they know he sold it then they might as well remove it from his downloadable games list.
So really, there is nothing to worry about. If you don't download the game then there is only a your word against my word case, which I doubt a company would waste money on (then again, could be wrong...) and if you do redownload a game you sold, evidence of deleting a previous copy wont save you, as it is a recently downloaded copy they are bringing up.
Still think it's messed up that the act is written in such a way to put the burden of proof on the seller,as they're being asked to prove something impossible to prove. Granted, since it is a civil case a video recording of the entire process would probably work more than well enough.
Hopefully that made sense, it's late here.