Dozens of police officers swarmed protestors from the activist group Code Pink outside a main entrance to the Republican National Convention Tuesday, because they were holding tennis balls.

In June, the City of Cleveland added tennis balls to its list of prohibited items inside a 3.3 square mile “event zone” surrounding the Quicken Loans Arena. Other prohibited items included tape, rope, bike locks, and any stepstool that could be used to address a crowd. But the prohibition did not apply to guns – meaning that convention attendees and onlookers are allowed to openly carry firearms, including assault weapons.

Cleveland police requested that Ohio Gov. John Kasich suspend open carry laws inside the “event zone,” but he denied the request.