A new patch is now available for Rocket League, updating the motorized footie game to version 1.12 (thanks PC Gamer). There are complete patch notes on the official website explaining that among other things, this implements bans for players who have altered their local game files:

CHANGES AND UPDATES

Online

• Implemented automatic timed matchmaking ban system associated with players who delete content from their game files to avoid competitive matchmaking in certain arenas.

BUG FIXES

• Skill Rating calculation has been fixed on the League Rankings screen and now accurately reflects your MMR
• Fixed an issue that caused the Ranked Reconnect popup to appear improperly during gameplay
• Fixed an issue that caused players to lose input in the Muting menu
• Competitive games are now properly labeled on the in-game score card
• Players will no longer incorrectly appear to be in a party on the scoreboard
• Fixed an issue that allowed Ballcam to be enabled/disabled erroneously in the post game screen
• (PS4) Players can once again view their old replay files
• (PS4) Text Chat keybinding has returned to the Controls menu
• (PC) Fixed an issue that displayed party members cars incorrectly in the main menu
• (PC) Fixed an issue with how the Max FPS slider capped frame rate
• (PC) Fixed an issue causing users with large Steam Friend Lists to experience graphical hitches