This would work (albeit in a demoralizing way) in corporate America. I don't think it's going to work when his cofounder also owns the code base and the OP does

This would work (albeit in a demoralizing way) in corporate America. I don't think it's going to work when his cofounder also owns the code base and the OP doesn't really have a right to restrict him. This is a communication problem, not a technology one.