Johnny C. Taylor, Jr.: In most cases, employers can require the use of PTO and limit when an employee may use it.
There are a couple of reasons your employer may require employees to use a certain percentage of their PTO each year. The first is to encourage employees to take time off in pursuit of healthier work/life integration. This practice signals to employees that their lives outside of work matter and they are not expected to be connected to the office 24/7/365. Employers also understand that workers who take time away are more productive in the long run—and also tend to stay with their employer longer.