There's nothing illegal about it. Poor management, yes.
But why he's punishing the entire department is beyond me. Is it a case that they cannot keep up the workload, or is it a case that the management is trying to get more business hopefully by opening up for additional hours?
I'm in HR, and as far as I can tell, there is no federal guidelines governing the hours you have to work. However, unless you are salaried exempt, they do have to pay you 1.5 times your hourly rate for any hours over 40 per week. Your only course of action is to look at your employee handbook and/or your employment contract (if you have one). Is there anything in there that shows your manager is violating company policy.
Otherwise, you have to realize that in this tough economy, employers are gonna push the envelope, because they know that there are people who will be happy to get hired in your place. So, if they can get someone to quit because they don't like the working conditions, they don't have to pay them unemployment.
EDIT: Dan B's information is absolutely correct. Make sure you are documenting the hours worked. Your manager cannot require you to work hours that you are not being paid for. If you are being required to work hours that you are n ot being paid for (and are not salaried exempt), then you have a situation that can be taken to the state's Wage and Hour division. Just make sure that you have accurate documentation, including dates and times.
However, if you are salaried exempt, it means that you are exempt from the provisions of the National Labor Relations Act and that means that you really have no legal recourse, because you are exempt from labor laws governing hours worked and overtime statutes.