This is not in dispute. What is in dispute is the gratuitous possession of land that is not needed for the federal government to function. If the Feds don’t need it, why do they have it? And likewise, why would any constitutionalist argue for a larger federal power when it is not necessary?
The land in question is within the Lake Mead National Recreation area (Hover dam). In fact, the nearest boarders are about 5 miles apart between the land and the lake. Size and scale out west are sometimes not understood by those who live out east. 5 miles is considered next door relatively speaking.
So as for “needful” this area can be described as having a number of needful buildings. Including power plants, ranger stations, maintenance buildings, and even Dock-yards. Yes I know some people do not understand the definition of dock-yards and try to make fun of the situation but there are docks and surrounding support buildings, thus dock-yards. Heck there is even a coast guard auxiliary on Lake Mead.
Because it's their's?