What National Park "laws" are you referring to? (I don't think the National Parks can make laws. That's a function of the legislature, but they can make regulations. Someone please correct me if I'm mistaken.) All I was able to find is this: "Policy Memorandum 14-05 (“Unmanned Aircraft – Interim Policy”) requires all superintendents to insert closure language in the park compendium prohibiting launching, landing, or operating unmanned aircraft from or on lands and waters administered by the National Park Service (NPS), subject to the exceptions and conditions described in the Policy Memorandum." Note that "operating...
on lands" is included in addition to "launching" and "landing". Elsewhere in the Memorandum this language is used"...to use the authority under 36 CFR 1.5 to
close units of the National Park System to launching, landing, or operating unmanned aircraft...". We could argue that if we aren't ourselves on park land then we are not operating on park land even if we're flying over it. I would be very surprised if that was the intent of the regulation or that a court would it interpret it that way. It isn't worded all that precisely, IMHO.
The sentence I quoted comes from here:
To:
www.nps.gov/policy/PolMemos/PM_14-05.htm
I understand this to have been a temporary Policy Memorandum from June, 2014. I don't know that it has been updated.
If you have some specific information you can quote, some actual rule or regulation you can reference that supports the notion it's OK to fly over National Parks as long as you launch from outside their borders, I'd very much like to know about it because there are probably some parks I'd love to fly over. Is it possible you're just passing along something you read or heard that wasn't official?