At common law, employee-employer relationships that were not controlled by a formal contract were considered at-will relationships. Employees could be dismissed for any reason at all, whether the reason was discriminatory or not.
Today, the at-will relationship between employee and employer is still a common one with employees not working under a union contract or some other form of agreement. However, the at-will term has become somewhat misleading, since a host of federal laws and rules now govern the employee-employer relationship. Perhaps the most important in terms of protecting employees against arbitrary dismissal by employers are the civil rights laws.
When arguably the most important of these laws—the Civil Rights Act of 1964– was drawn up, many advocates of the law felt a gatekeeper was needed to prevent the courts from being clogged with employee lawsuits under the new law. This led to the creation of the EEOC, which was given primary responsibility for the enforcement of these laws. Subsequently, the EEOC was entrusted with the enforcement of practically all civil rights laws, with the exception of federal employees, who are protected under the 1978 Civil Service Reform Act. Enforcement of that act is entrusted with the Office of Special Counsel and the Merit Systems Protection Board.
The size of the employer determines if it falls under EEOC authority. Employers of 15 or more employees are covered under both Title VII of the Civil Rights Act and the Americans With Disabilities Act(ADA). Employers of 20 or more are covered under the Age Discrimination Employment Act (ADEA), and the Equal Pay Act has no limit in terms of the size of employers it covers.