CoD Wars 2.0
Possession is 9/10ths of the law, and the government cannot get around that in any way other than passing additional laws.
I guess it's also how national laws would fit with international laws and treaties, eg collective punishment, or violations of human rights due to seizing property, or aspects of WTO etc.
But it would seem as though there are potential alternatives. ISTR the venerable Castle Wolfenstein being banned/illegal in Germany due to depictions of Nazi insignia, and the same happening with other games. I think Rimworld also got in trouble because it allows cooking with ingredients that are illegal in Germany. I think Australia has pretty strict laws banning some games due to canniibalism and other potentially offensive activities. And I guess the UK could ban games that featured torture or even Civilisation given it's a popular genocide simulator.
Then I guess it could just declare some titles are Video Game Nasties and make the sale/supply illegal, along with punitive fines, should they be caught doing so. Or selling age-restricted games to kids. Or I guess for 'cloud' games, illegal/unenforceable contracts with minors, if games require monthly service payments. And then there'd still be all the potential for competition and market distortion. I guess blocking the merger is just pre-empting some of that already existing illegal behavior.
Personally I think it's in many ways a good thing, if it discourages predatory behaviour from Big Tech. So turning games that you used to be able to 'buy' for £39.99 and play whenever and whever you want into £79.99 games + £19.99 a month for a game that you may just want to play on a beach somewhere. But instead it forces you to be online so it can bombard you with offers for level-ups, power-ups, DLC packs and generally try to hook people on pixel crack. Or the game will use it's camera directors to force your character to keep looking at ad hoardings or billboards for whatever carp it is that MS's adsense division is trying to flog you.