Many startups are exempt from even that. The Federal Age Discrimination in Employment Act applies to companies with 20 or more employees. Some states have stricter rules (5 employees or more for the California Fair Employment and Housing Act).
Companies here are so litigation-averse that they’d never fire someone outright for being too old. They have an entire department (HR) to help build a solid, believable paper trail for firing them for “performance issues”.
> The Age Discrimination in Employment Act of 1967 (ADEA) protects certain applicants and employees 40 years of age and older from discrimination on the basis of age in hiring, promotion, discharge, compensation, or terms, conditions or privileges of employment.
Are you maybe referring to a different federal law?