who are the Entertainment Software Association?

I'm seeing this pop up a lot saying the downloads were taken down due to this generic association. It's popped up for DKC on GBA, Metal Gear Solid on GBC, and Pac-Man Special Color Edition ect. Weird because other games like Sonic are supposidly removed by Sega and Mario is removed by Nintendo. Who the heck are the Entertainment Software Association? Some hacker group? Bots?