Many workers are hired on an at-will basis, meaning they have no contract and can be fired -- or can quit -- without a reason. This can't be done illegally, of course, meaning that workers can't be fired based on ethnicity, gender, or other protected classes. However, it means employers don't necessarily have to have a reason for the firing.
This changes when employees are given a contract specifying that the employer must show cause. Then, if the employee is fired for no reason, he or she may be able to claim it was arbitrary and start a lawsuit.
While many employees who simply apply for jobs may not dictate their contracts, high-profile employees could ask for this clause, for example. It's a way for them to protect their jobs. Employers aren't obligated to give them the clause, but those who do must then abide by the contract.
When the whole thing can get complicated is when there is not an official contract, but when the employee claims there was an implied contract. The employee can then say that he or she was led to believe cause was needed, even in an at-will employment situation.
For instance, in some previous cases, employees have been given handbooks upon hiring that said termination would only be done with cause. Even though that was just in the handbook and not the contract, courts have said that set up an implied contract, meaning a termination without cause was illegal.
Employee rights can be complex, but it's very important to know what they are. All those who feel they've been unfairly and illegally fired need to know what they can do in court.
Source: Cornell Law School, "Wrongful termination," accessed Feb. 24, 2017