If it's HS yell time and enforce the balk. In any other rule set, yell that it is a balk and and let it go. At the end of play decide whether it is ignored or enforced.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .