A more thorough explanation:

A deferral state is a state that has its own anti-discrimination legislation and enforcement mechanism under the Age Discrimination in Employment Act (ADEA). This means that the time to file a federal lawsuit under the ADEA is postponed until state remedies have been exhausted.

For example, if an employee in a deferral state believes they have been discriminated against based on their age, they must first file a complaint with the state agency responsible for enforcing anti-discrimination laws. Only after exhausting all state remedies can the employee file a federal lawsuit under the ADEA.

This process ensures that the state has the opportunity to address the issue before it is taken to a federal level. It also allows for a more efficient use of resources by avoiding duplicate investigations and potential conflicting outcomes.