Monday afternoon, the U.S. Senate will gavel to order the first congressional hearing on a D.C. statehood bill in 21 years. No, the fact that the New Columbia Admission Act is getting a hearing doesn’t mean that its chances of passage have appreciably improved, but it doesn’t hurt the cause to bring new attention to the fact that nearly 650,000 American citizens do not enjoy congressional voting rights.

That attention can rub both ways, however. For instance, the hearing has renewed questions about the constitutionality of creating a state of New Columbia through an act of Congress, as the present bill would do. The thinking behind the New Columbia Admission Act goes like this: Congress has the explicit constitutional power to admit a new state, and it has the power to change the size of the District — after all, it gave the portion of the original “ten Miles square” lying west of the Potomac River back to Virginia in 1846 — so why not shrink the current District to a small enclave encompassing the White House, Capitol and military facilities, admitting the remainder of the city as a new state?

Such an approach has the advantage of requiring only an act of Congress — difficult, to be sure, but much less difficult than the alternative of amending the Constitution, which would require a joint resolution of Congress and ratification from 38 of 50 states.

But there are significant objections to the current approach to statehood from those who say that Congress does not in fact have the power to shrink the District. The constitutional provision for a capital enclave “ten Miles square” means “ten Miles square,” some argue.

How to make that argument square (pun very much intended) with the Virginia retrocession? Cato Insitute scholar Roger Pilon and historian and frequent Republican candidate Nelson Rimensnyder, point out that the Supreme Court never ruled on whether it was constitutional for Congress to give Virginia its portion of the District back. By the time the question was finally posed, in 1876, the high court decided it was too late to weigh in — Virginia had “de facto” possession, and revisiting the matter would be too disruptive.

Should Congress again act to change the size of the federal district, however, you can expect the matter to go to the courts forthwith. Statehood-bill skeptics find support in a 1964 memorandum from then-Attorney General Robert F. Kennedy that raised doubts about Congress’s power to pursue a Maryland retrocession without constitutional amendment — logic, they say, that would also apply to the New Columbia Admission Act.

There are other constitutional objections as well: Pilon suggests that Maryland could object to the establishment of a New Columbia, arguing that it “did not cede the land for the purpose of creating a new state on its border,” and also notes that the 23rd Amendment would need to be repealed, lest the tiny number of residents left in the federal enclave stand entitled to three presidential electoral votes.

All of this is not to argue that the New Columbia Admission Act isn’t a worthy goal for statehood backers to rally behind. But the constitutional objections mean that the already towering task of gathering sufficient votes in the House and Senate, as well as a presidential signature, might not be enough in the end to make D.C. statehood a reality.