This is not correct. They are bound by state labor laws for where they have employees based. That's in addition to federal labor laws.

For example, when we had an ONT and LAX base, the company at first refused me the use of my sick time for the illness of my child. Once I refereed the California Kin care law to our MEC attorney, he wrote a letter to the company making them aware of the law. The MEC issued an email explaining the benefit to us. Afterward, the company issued a memo stating the entitlement for California based employees only.