All states in the US, except Montana, have some form of at-will employment. However, some states have further limitations on top of federal laws, such as the public-policy exemption, implied covenant-of-good-faith and fair dealing exemption, and implied-contract exemption.

Montana is the only state that is not an at-will employment state. In Montana, employers can practice at-will employment during a probationary period only.

It is important to note that even in at-will employment states, there are exemptions and exceptions to the at-will doctrine. For example, public-sector employees are typically not subject to at-will employment, and when employment contracts are the subject of union bargaining, a common demand is that employees can only be terminated for just cause. Additionally, at-will employment does not apply if there has been a breach of good faith by the employer, or if an employee is terminated due to discrimination.