That’s right — it may be entirely legal (federally) to fire someone who wants to pump at work.
Milk: It Does a Business Good
Julia Kurnik

This is currently being tested in the courts. If you want to get in the weeds… The Pregnancy Discrimination Act of 1978 amended Title VII of the Civil Rights Act to “prohibit sex discrimination on the basis of pregnancy.” Although the Civil Rights Act outlawed gender discrimination, courts were finding that did not include pregnancy since that is a biological difference, not just gender. It also outlaws discrimination on “related conditions” to pregnancy. The question is whether lactation/breast feeding is a related condition… Lower courts have decided in both directions. There has only been a single appellate court decision on this, Houston Funding in the 5th circuit, which did decide lactation is included… so if you live in the 5th circuit, hurray! A case is currently in the 11th circuit on this issue. We will have to wait and see which way it goes, and if this makes it to the Supreme Court or not.