You can still play Xbox One games with a banned account
Given that Xbox One games will be tied to your Xbox LIVE account, there's some worry among gamers (the ones who break the rules) that having your account banned will result in losing access to games you have already purchased. The question became a concern when Xbox Support tweeted, "If your account is banned, you also forfeit the licenses to any games that have licenses tied to it as listed in the ToU." Although the question specified Xbox One, Xbox Support later clarified this answer was in reference to the Xbox 360.
Microsoft's Larry 'Major Nelson' Hryb refuted the notion, offering a more clear answer to the question: "Absolutely not, you will always have access to the games you purchased." In all likelihood, you'll probably still lose access to the multiplayer portion of the game.
So there you have it, future banned Xbox One users. Your games are safe, provided your Xbox One can connect to the internet once every 24 hours.