The Entertainment Software Rating Board is not a government entity. In fact, it was created in the 1990s specifically to keep Congress out of the video game industry, at a time when lawmakers were loudly condemning the infusion of digital violence in popular culture. The ESRB was modeled after the film industry's MPAA, doling out ratings for video games in North America. Back in the Clinton era, there were no federal laws requiring publishers to display ratings on their games, and there still aren't today.
The ESRB oversees the entirety of the video game ratings system, from AAA to independent developers and specialty shops like iam8bit, Special Reserve and Limited Run Games (which release physical editions of digital indie titles). This year, the ESRB announced a change to its rating policy that rocked the very foundation of Limited Run Games' business model.