overtime question

[web dev <programming95@yahoo.com>]

hi all,
  I have a friend of mine, who is brought over here to
the US on H1B visa. He is working in Atlanta. His
employer is asking him to work over time and on
weekends. (For no extra pay). 
  for personal reasons, my friend, feels that he will
not be able to do that. Can he do that. Is it legal to
say No to the employer about working on weekends.
Would it affect his employment? What does the law
say?. Is it like every employer can have his own
rules?

I know that this is not a Java question, but i thought
I would seek some advise over here. On H1B they are
like bonded labor and he is scared to put his question
on the net... thought i 'd do that for him. 

I 'd appreciate any inputs on this issue

Thanks all.

Sudhakar

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