While most people would like to think that they have the ability to remain at a job as long as they like and leave whenever something better comes along, this is actually not the reality for many. Though some people have agreements with their employer that provide them some protections from termination, the presumption is that employment is "at-will."
At-will essentially means that an employer is able to terminate an employee at any time without legal consequence, as long as the reason for termination is not illegal. This is the rule in every state except Montana. There are certain exceptions to the rule, though, which we'll briefly mention.
As mentioned above, the at-will rule may be modified by contract, as is common with executive level employees. Such agreements may require the employer to base termination on some good cause, such as misconduct, poor performance, or business needs. Such categories can be broadly or narrowly defined, but it does provide some protection.
There are also statutory exceptions to the at-will rule, such as those dealing with illegal discrimination, retaliation, and whistle-blowing, as well as protections for certain off-duty activities. Common law exceptions also exist, depending on the state. Such exceptions may be based on things like public policy, contract law, tort-based claims, and equitable relief.
For employers, it is important to work with an experienced business law attorney to receive guidance drafting and negotiating employment contracts containing provisions which modify the at-will rule. An experienced advocate can also advise an employer on managing employee expectations concerning the employment relationship.