My justification for what exactly?

Selling keys you were gifted to play in order to raise the games profile. See your previous comment if you’re still confused as to what’s being talked about.

If theres no formal agreement and no contract between the dev and the recipient of the key, where/what is the crime??

As I literally just said, if your justification is that it isn’t a crime, you already know it should be. Seeing as you seem genuinely confused, verbal contracts and agreements in writing (e.g email exchanges) are still contracts, even if not formal.