Assuming that you are in the US, the answer to your question is yes, the employer can. There is nowhere, anywhere in the US, where an employer is required by law to provide paid vacation. So in the absence of a legally binding contract or CBA that specifically says otherwise, the employer may suspend or downright cancel paid vacations any time he chooses. He also may legally refuse to allow employees to take paid vacations, even with time already accrued, with the same caveat.
However, depending on what state you live in, the employer might or might not have to pay you the value of any vacation already earned at the time of the suspension. Since you chose not to follow the rules of the forum and provide us with the name of your state, whether or not that is the case for you will have to go unanswered.