Twitter CEO Dick Costolo, who is also a Michigan football booster, committed a minor NCAA violation this weekend when he tweeted his support to a 5-star prospect who committed to the school.

Because of Twitter’s popularity–athletes and recruits are constantly on the social media site–the NCAA instituted some rules to prevent boosters from communicating with recruits on Twitter.  

After high school wide receiver George Campbell committed to the school on Saturday for the Class of 2015, Costolo was following the chatter on Twitter. When he saw Class of 2014 commit Wilton Speight tweet “welcome to the family” to Campbell, Costolo jumped in the conversation, tweeting at Campbell, “amazing! #goblue.” 

@WiltonSpeight @GeorgeCampbell0 amazing! #goblue

— dick costolo (@dickc) July 29, 2013

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That, per NCAA rules, is a minor infraction because Campbell has not yet signed his letter of intent with the university. As CBS Sports explained, “According to one of the roughly billion rules the NCAA has, a booster is not allowed to contact a recruit until after the recruit has signed his letter of intent with the school. Not in person, not on the phone and not on social media.”