§623. Prohibition of age discrimination
(a) Employer practices
It shall be unlawful for an employer—

(1) to fail or refuse to hire [...]
    any individual[...]because of such individual's age;

(f) Lawful practices; age an occupational qualification;
    other reasonable factors; laws of foreign workplace;
    seniority system; employee benefit plans;
    discharge or discipline for good cause
It shall not be unlawful [...]

(1) to take any action otherwise prohibited[...]
where age is a bona fide occupational qualification
reasonably necessary to the normal operation[...]
or where the differentiation is based on
reasonable factors other than age[...]
or where such practices involve an employee
in a workplace in a foreign country, and compliance
[...]would cause[...]to violate the
laws of the country in which such workplace is located;