I wouldn't personally lose sleep on whichever way loot boxes were legislated. If their contents are easily converted into real-world cash, I would say the company bears some responsibility for the actions of any black markets, perhaps proportional to the volume traded. CS:GO has to crack down on its massive skins market, Kinder doesn't have to sweat its little toys.

Generally, I think the common-law notion of "consideration + chance + prize" augmented with the requirement of an "insurable interest" (in order to keep the insurance industry legal) discerns the truth well enough. Insisting that any "prize" not be monetary or monetarily-convertible keeps it from becoming a cyclical addiction, and evaluating infractions relative to volume keeps extremists from banning gumball machines and Kinder eggs.