If I own 25% of a franchise, my partner owns 25%, and the third partner has 50%, who is able to call the shots.

Good question.  You and your partner together own 50% and the third partner has 50% ownership.  The third partner does not have 51% of the ownership and you and your partner together do not own 49% ownership.  It is tie vote! Therefore, he does not have the ability to do whatever he wants to do, especially if he is breaching his fiduciary duty to the company.     You need to review your By-laws or Operating Agreement, to determine how to break a tie vote.  It is always a good idea not to set-up an orgainization that can result in a tie vote. That's why you would want an unever number of Board members.    I once had clients who insisted they they wanted their structure to have a tie vote, against my advise.  In order to have a method to break any tie, we put together an Operating Agreement that stated any tie votes would be decided by a flip of a coin.  This is probably not your case.