Laws are different for country to country obviously, but even more confusingly in America, I believe they also change state to state.
Here in New Zealand you must be 16 before you can work full time. I guess theoretically you can get a part time job anywhere assuming an employer will take you on.
Unfortunately right now, New Zealand businesses nationwide have taken the really annoying approach of only wanting people with years worth of experience, even in the basic jobs of certain fields and industries. There is no room for young people wanting work experience, or even newly qualified people trying to get on the job ladder. Its a real problem here.
So the only issue might be if the company can be bothered to take on someone young.