Vacation time approved, then denied

Over a month ago, I submitted a request for a week's vacation in mid-August. (I have more than a week's paid vacation accrued.) Today my manager informed me that all vacations for employees in my job function, including vacations that have already been approved, will be suspended until we reach a certain milestone. This milestone will probably not be reached until late August or September.

He said that the company would compensate for any money lost because of changed plans, e.g. hotel deposits, airline change fees, etc. Despite that, I am unwilling to change my plans for personal reasons - I would be letting down people about whom I care very deeply.

Do I have a legal right to take this vacation? Could the company fire me if I refuse to change my plans?

The following are related excerpts from the employee handbook, which I signed when I accepted this position:
"When you are planning to use vacation time, you must complete a Time Off Request form that includes authorization from your manager. These forms should be submitted to payroll no later than two weeks prior to the date requested. <Company name> encourages employees to take time away from work; however, must retain the right to deny requests for time off based on business demands."

"As a general rule, employees may not take payment in place of vacation. Exceptions to this rule are possible if business demands do not allow you to take your vacation."

State: Minnesota

I don't think you have a leg to stand on. They gave you ample warning in the handbook, etc. If you insist on taking this vacation time, then you might be issued discipline, put a severe dent in your "up the ladder" climb within the company and/or be fired. Vacation is a benefit and there is no law that I know of that states that it is illegal for a company to move it around as their business needs dictate.