I've been given 4 weeks of personal leave as a company benefit and am an exempt salaried employee, but have a standard 40 hour work week. However, if I use more than 2 weeks of the personal leave during the year, I'm expected to work longer hours or weekends to make up for the additional leave taken. Is that legal for my employer to expect that? He expects that of about 60 of his employees.

Yes, it is legal because there is no law that prohibits it. If, as an exempt employee, you are expected to work some additional hours because you are taking time off, the employer is within his legal rights to require that you do so.

It's not illegal.

If an employee works 40 hours a week, 52 weeks a year, it totals up to 2,080 hours in a year. Most government contracts are bid with employees working anywhere between 1,920 and 2,000. It sounds like yours was bid at 2,000 (2,080 minus 80 for two weeks of vacation). If you take two weeks vacation and don't make up the hours, that's 80 hours of your time for which the employer must pay you and for which it cannot bill the client.

Thus, it's not unusual to expect employees in a government contracting situation to work a set number of hours per year to ensure profitability on the contract. Most of us who work on contracts just throw in an extra hour here or there with no problem and don't have a problem reaching the hours over the course of the year.