My question involves labor and employment law for the state of: Virginia

Here is my inquiry:

If a waitress/waiter requests a week and a half off for vacation is it legal for the restaurant to not schedule the person after they come back? For example:

The restaurant is extremely busy during the summer time and one of the waitress/waiter(lets just use "John") requests 2 weeks off to go traveling through Europe. Is it legal for the restaurant to hire someone else for that position and not give John his job back when he returns?