Originally posted by mwmillerMoreover, if you want to stop challenges from a specific player, you can add him to your Ignore list.
In addition, you can change your settings to prevent someone from challenging you.
On the top navigation bar, go to "My Settings / My challenge settings."
You can set the limit to zero or any number you prefer.
Once you have that set to what you want, make sure you click the "update" button on the bottom of the page before exiting that page.