Your friendly gov worker will happily tell you the legal basis for their entry if you ask them. There may be something in place contractually that your Dad set up with the Feds that your Mom is unaware of. If they can’t answer your question, tell them they need a warrant and contact your congressman same day.
The land is in a family held corporation. We have no such deals or understandings with the feds.
The fact that the Heinz famiy is associated with this gives me the heebie jeebies.