At-will Employment

Massachusetts law still recognizes the at-will employment doctrine. However, it is more accurate to say that Massachusetts employers may terminate non-contract employees (most of us) for any legal, non-discriminatory reason. So, as obvious examples, an employer cannot fire someone because of their race, age, gender, etc. There are also numerous federal and Massachusetts statutes that prohibit termination for certain specified reasons. For example, under Massachusetts General Law Chapter 149, Section 6D, no employee can be terminated or punished for filing a complaint regarding the ". . . occupational health and safety of such employee or other workers engaged in the use, handling, removal or disposal of asbestos."  Similarly, an employee cannot be fired for asserting legal rights or doing that which the law requires.
 
Also, there is case law in Massachusetts that clarifies and establishes exceptions to the at-will doctrine. In GTE Products Corp. v. Stewart, 421 Mass. 22 (1995), The Supreme Judicial Court recognized the concept of Constructive Discharge, where an employer with an unlawful motive harasses or alters an employee's working conditions, forcing her to resign.  Hope that helps.