[Pedestrian]

Originally Posted by JManc

It would be a long drawn out court battle and VA would win. The federal government has no authority over existing state boundaries (states are sovereign)...other than create new states so VA would have to be willing to return Alexandria back to DC. MD/VA volunteered the land initially. Both sides agreed to retrocede the land back to VA...

I'll repeat what I said: It's likely a political impossibility and Constitutionally dubious. So we don't disagree MUCH. You are right that the federal government has no authority over state boundaries with this single possible exception since this bit of Virginia actually WAS ceded to the Feds by Virginia as a result of a historical deal and then returned to it by the Federal government. Could that government take back their action returning it? That's for the lawyers.

A little history:

On December 23, 1788, the Maryland General Assembly passed an act, allowing it to cede land for the federal district. The Virginia General Assembly followed suit on December 3, 1789. The signing of the federal Residence Act on July 16, 1790, mandated that the site for the permanent seat of government, "not exceeding ten miles square" (100 square miles), be located on the "river Potomack, at some place between the mouths of the Eastern-Branch and Connogochegue" . . . . (It) limited to the Maryland side of the Potomac River the location of land that commissioners appointed by the President could acquire for federal use.

The Residence Act authorized the President to select the actual location of the site. However, President George Washington wished to include the town of Alexandria, Virginia within the federal district . . . .

The U.S. Congress amended the Residence Act in 1791 to permit Alexandria's inclusion in the federal district. However, some members of Congress had recognized that Washington and his family owned property in and near Alexandria . . . . The amendment therefore contained a provision that prohibited the "erection of the public buildings otherwise than on the Maryland side of the river Potomac" . . . .

After a referendum, Alexandria County's citizens petitioned Congress and Virginia to return the area to Virginia. By an act of Congress on July 9, 1846, and with the approval of the Virginia General Assembly, the area south of the Potomac (39 square miles; 101 km²) was returned, or "retroceded," to Virginia effective in 1847.

https://en.wikipedia.org/wiki/Histor...ashington,_D.C.

So that's how DC was created and later modified and, as I said, I'll let the lawyers argue about whether any of the legislative acts, state or federal, could be undone. One point though--that it did take acts of the state legislatures for the land to cease being parts of Maryland and Virginia originally shows JManc is correct that the Feds couldn't just take it or any part of any other state, but having been given it once could make it unique.