(FORTUNE Magazine) – There's a splashy cocktail party Saturday evening, and all your important clients will be there. You can't make it (sorry, prior engagement), so you ask that smart guy down the hall who works for you. He's great at these things. Trouble is, he's not particularly happy about going. In fact, he downright resents being asked to do the company's bidding on his own time. Still, the boss is the boss, so he keeps his grumbling to himself and complies. Is it right for you to have asked him in the first place?

Legally, if he's an hourly employee, the request may run afoul of labor laws, which require that employees be paid for all company work--at time and a half for anything more than a 40-hour week. But for salaried employees, labor laws offer no guidance.

Ethically, it's a bit more complicated. There's nothing wrong with asking salaried employees to volunteer to do company business on their own time. But the operative word is volunteer.

More often than not, when you suggest that an employee attend an outside event, there's subtle coercion involved simply because you're the boss and, well, the employee's not. When you take advantage of such inequality in power, you cross an ethical line. The voluntary nature of the request needs to be made absolutely clear. If it goes unsaid, it's a fair bet the employee will assume there's more at stake than just the time lost. That's when you've gone too far.

It's also reasonable for employees who work overtime to expect the company to yield a bit to their personal business--whether it's allowing a longer lunch or some surfing time on the company Internet connection. As long as they're not mining the company's databank for a competitor, there's no harm done.

Ultimately, it's a question of fairness. If the company blurs the line between work and personal life, then it's only fair that the employee would expect to do the same. The wisest course is to set parameters on both sides and trust that each party will be less inclined to take advantage of the other.

JEFFREY L. SEGLIN teaches at Emerson College and is the author of The Good, the Bad, and Your Business: Choosing Right When Ethical Dilemmas Pull You Apart.