Well, no, because you can't process a transaction that is related to, or a byproduct of illegal activity. This goes without saying, and is built as part of US in consumer/business law. So that being known, "Under any circumstance" would only apply to lawful, legal transfers, by default. Despite it saying 'any circumstances', steam is not allowed to participate knowingly, or unknowingly, in criminal activity, they are a business, a legal and above board business. And when they do discover the illicit activity, they take the corrective measures to secure their micro-economy.
lets say Tyrone sold you a stolen car. You wrote it all out on the back of your mcdonalds napkin.. "Kontrat... tyron 2 sel jaqueel 1 honda civic for 2000 dallars $$ bling bling"
now you pay tyron but he doesn't deliver.
Good luck calling the cops. Lets see how far that gets ya. The fact you were involved in illegal activity makes the contract null and void. No court would hear it.
Now I agree the wording is poor here, but its also effective. More educated readers will see it as I do, the same way we see the Walmart "no questions asked" return, of course they'll ask questions! Especially if you bring back a bike you bought.... as a cube... "sir, what happened to that bike, its now a 3"x3"x3" cube?" "that doesn't matter, i want to return it, i'm not happy with this product" ... yeah good luck with that one. They've got to look out for their best interests, as a business. Where as, the majority of readers would think they have a good deal, and security in their purchases and think they can return anything/everything however the condition. and most are right, and will have no issues. The sketchy kids are the lousiest little shits on here, every time you see another one of these post.. "oh noes... i was trading with a guy i found off tor, he sounded like he was russian, i dont care, he gave me six copies of gta 5 for 3 trading cards... and now my account worth a gajillion dollars is banned... woe is me... pitty pitty pitty... i'm a stupid shit that thought i could game the system..."