http://www.pcgamer.com/belgium-may-classify-overwatch-and-star-wars-battlefront-2-as-gambling/

The ESRB said in October that loot boxes, despite their inherent randomness, are not a form of gambling. A couple of days later, PEGI and Ukie agreed. Shortly after that, so did the UK government, although somewhat less firmly, and with a promise to "continue to monitor developments in the market." Developments, perhaps, like the Belgian Gaming Commission's announcement that it's investigating whether Overwatch and Star Wars Battlefront 2 should be classified as gambling. 

The issue, of course, is the inclusion of loot boxes. As VTM News (Google translated) notes, you play the game to improve your character, or if you're lacking the time or inclination, you can throw money at it and pop some box tops. And that's the problem: You're spending money, but you don't know what you're getting. The system is "dependent on chance," Gaming Commission director Peter Naessens said, which is why the games are now under investigation.