Mojang, the Swedish game developer bought by Microsoft (MSFT) two years ago, wrote in a blog post on Tuesday that advertisers are no longer welcome inside its signature game where more than 100 million registered users spend time building landscapes and structures.

Mojang published new “Commercial Usage Guidelines” for Minecraft, one of the world’s most popular video games, that ban companies, advertising agencies, and other groups from using gameplay to promote their brands or causes. Owen Hill, Mojang’s director of creative communications, wrote in the developer’s blog post that Minecraft‘s ever-growing number of users means “that Minecraft has become a viable place for companies to advertise unrelated products or for organizations to promote their causes.”

Now, Microsoft and Mojang want to block users associated with brands from using the game for the purpose of “selling an unrelated product.” As examples, Hill includes such unwanted scenarios as restaurant chains building virtual models of their restaurants using Minecraft blocks, or movie studios using the game to recreate the fictional world from their films.

“It’s worth mentioning that fans of a particular restaurant, movie, or some other thing are still free to build things in Minecraft that represent or celebrate it so long as the goal or focus is not to promote or sell that stuff,” Hill writes in the blog post. The new guidelines apply only to companies or other groups—even non-profits or politicians—that want to use Minecraft to sell products or promote causes, and they also can’t hire someone else to create in-game ads, either.

The new guidelines also note that companies can still pay to advertise within designated ad windows that pop up in Minecraft videos or buy ads on Minecraft YouTube videos.

Since paying $2.5 billion to acquire Minecraft developer Mojang in 2014, Microsoft has worked to expand the massively popular game’s audience, including by promoting the game as an educational tool. And just a couple of weeks ago, the companies announced that the game will soon reach an even greater audience as part of a deal to publish Minecraft in China following a long regulatory delay.