In the USA, in Sega v. Accolade the judge ruled that you can't use a trademark to block access to your stuff. The context was, the Sega Genesis DRM had a check for the string "SEGA" somewhere in the game's ROM; presumably, Sega reasoned that they could license their trademarked name for this purpose to licensed devs and sue makers of unlicensed cartridges for trademark infringement; and did sue Accolade when they attempted to publish unlicensed games for copyright and trademark infringement. The appeals judge overturned an earlier decision in favor of Sega, citing that trademarks can't be used to block what would otherwise be a fair-use act.

Much of Sega v. Accolade was overruled by the DMCA, which explicitly makes defeating DRM a crime in the general case. But the prohibition against using trademarks to gatekeep people performing legal, nonfraudulent activity probably remains and may be cited in future cases.