[Bob]

I'm assuming you mean this portion:

...and to exercise like Authority all Places purchased by the Consent of the Legislature of the State in which the Same shall be, for the Erection of Forts, Magazines, Arsenals, dock-Yards, and other needful Buildings;

That's one huge penumbra, or is that an emanation?

Does that seem anything close to what makes up federal land today? How much of that area is actually being used for its specific intended purposes?

[Tolerance Sucks Rocks]

Does that seem anything close to what makes up federal land today? How much of that area is actually being used for its specific intended purposes?

And how much of it was obtained with the actual permissions of the state legislatures?

[Ben Ficklin]

That is referred to as the "enclave clause", and is not applicable.

Instead, the courts use the "property clause"

Federal lands are managed in accordance with the acts of congress and the main one is FLPMA in 1976. The Taylor Grazing Act, Endangered Species Act, and a few others also play a big part. Other lesser acts also come into play, like wild and scenic river act or the Wilderness act.

The Land Agencies are like all federal agencies, they have a large number of lawyers to interpret acts of congress, court decisions, and negotiated agreements.