Boss wants an unrealistic amount of notice before I switch jobs I work in an industry that is very niche (maybe 50 locations or less in the world).  I've been here for over 3 years but have reached the end of my rope. A potential job offer is coming my way that I intend to go for in an entirely different. He threatened the person who had my job before me with calling their next employer and giving them an unsolicited poor review. Is this legal? Is there anything I can do to protect myself? 

