Employees who are hired for an indefinite amount of time are usually considered at-will. The employee can leave at any time; the employer can also terminate the employee at any time. However, there are exceptions. Terminating an at-will employee under the following conditions could get you in legal trouble:
Discrimination – it is illegal to terminate workers because of their age, race, religion, sex, national origin or a disability that does not influence their job performance.
Public policy – it is illegal to terminate a worker for reporting violations of the law or acting in the public interest.
To read more, see the article from CPA Practice Advisor.