A more thorough explanation:

The inevitable-misappropriation doctrine is a legal theory that states that a former employee, who has confidential information, cannot avoid using that knowledge to unfairly compete against their former employer once they are hired by a competitor. This doctrine is often used in trade secret cases to justify an injunction against the former employee.

For example, if an employee who has access to a company's trade secrets is hired by a competitor, the former employer may seek an injunction to prevent the employee from using that knowledge to compete unfairly. The former employer would need to prove that the employee has confidential information and that it is inevitable that the employee will use that information to compete unfairly.

However, most courts have rejected this doctrine because it effectively turns a nondisclosure agreement into a noncompetition agreement. The leading case upholding the doctrine is PepsiCo, Inc. v. Redmond, where the court compared the situation to a coach whose player has left with the playbook to join the opposing team before the big game.

Overall, the inevitable-misappropriation doctrine is a controversial legal theory that is rarely used in practice.