Doing something by Executive Order doesn't make it so forever. Anything that one president does by EO can be reversed by the next president on his first day in office.
Generally what you say is true...
But when they tie it into a UN agreement / International Heritage Site / World Natural Treasure site things get much more complicated.
And just how many Executive Orders HAVE actually been overturned in the entire history of the United States?
(I only know of two important ones)
And how many do you think that any Republican Presidents following McCain (in the unlikely event that there ARE any Republican Presidents following McCain) will overturn any that he made?
For all effects and purposes Executive Orders, by tradition are permanent, even though by force of law they COULD be overturned.