On the federal level, the Age Discrimination in Employment Act (ADEA) prohibits employers from discriminating against employees or applicants based on their age who are at least 40 years old. This law protects employees by ensuring that employers treat employees over and under the age of 40 years old the same. For example, employees over the age of 40 must also be eligible for the same benefits as their younger counterparts, including health insurance and retirement packages.