So, YouTube is a big, weird thing that people are still trying to 'figure out', especially in terms of legality. There are a ton of controversies that pop up around things like fair use and criticism, but this one is really quite something, and is pretty firmly in the "shady" collumn.
There is a lot of noise surrounding TmarTn and ProSyndicate at the moment, regarding the site CSGOLotto. The site essentially lets you buy keys with real money that then open chests that somewhat randomly outputs CS:GO skins, some of which can be worth up to the thousands of dollars. Sounds like a slot machine, right? It kind of is, but the item output isn't money (despite outputting items that can be sold for money), kind of like how Pachinko loopholes work in Japan. The first problematic thing? Unlike slot machines, there is no age enforced age restriction on the site, essentially creating a place where kids can gamble. Valve have come under-fire for this by Bloomberg for facilitating sites like these, by allowing Steam accounts to be attached to the websites, thus giving you the items. It doesn't look great.
Here is where it gets pretty wild though. ProSyndicate and TmarTn are pretty massive YouTubers with millions of subscribers. Syndicate is one of the biggest UK YouTubers, full stop. Well, they uploaded videos of them winning thousands of dollars in these gambling packages, thus encouraging their users to use the site. The problem? Well, as discovered by HonorTheCall, TmarTn is actually the president of the CSGOLotto, and ProSyndicate is the Vice President, something neither openly disclosed prior to this revelation. Both have acknowledged the controversy with Syndicate releasing this apology, although, if you go on TmarTn's account he does openly say "LOL" to a meme about enticing minors to gamble.
What happens now? Who knows. Legally, who would call the lawsuit? Is there other cases like this? What would actually happen? Would this be legally judged as gambling? Who knows, but right now it is a mess for loads of people.
If you want to get the lowdown in video form, h3h3 have a great breakdown on the situation.