Does any state in the Union not have at-will employment? What about Canada?
This site gives a pretty clear explanation of why there isn’t a clearcut answer by state in the US.
http://employeeissues.com/at_will_employment.htm
Not sure about Canada.
Basic answer: Yes. Exceptions to the doctrine vary by state. http://www.bls.gov/opub/mlr/2001/01/art1full.pdf (reviewing law nationwide).
According to Wikipedia, in Canada, employment for an indefinite term can only be terminated on “reasonable notice” or for “cause”. http://en.wikipedia.org/wiki/At_will_employment
Was going to copy and paste more, but it is a short article, and that just would not be fair.