My brother's employer is claiming that he is a salaried employee in order to get around paying him overtime. Is this legal?

You may be right. He should call some of us labor and employment lawyers. Misclassification cases can be tricky. There are often many defenses to them. He needs to decide what is in his own best interests and only then does HE get to decide what he wants to do. We love those cases because if the facts are good we can recover his attorneys fees from the employer and often liquidated damages. But he needs to decide the goal. Suggest that he call some of us to discuss. No point in him going to a lawyer's office if he does not see it the way you or I might. It's his job right? Most of us can figure out in a few minutes 1) Does he have a potential claim that we might win and 2) what is his goal long term. A phone call costs nothing.