Here in GA, you can fire anyone for anything as long as it's not due to age, race or religion. And I hate to say it, but if you're firing an old black Muslim for poor job performance, you better have all your ducks in a row and everything documented.
Personally, as HP said, I think that if they're not getting their work done, surfing ESPN is minor. Have a chat, tell them they're history if they don't start getting their work done, give them 30 days to prove themselves and go from there. Too many people out there looking for jobs to pay for mediocrity.