A group of 47 academics from top U.S. universities lambasted a proposed bill that would determine Puerto Rico's territorial status through a convention process.

In a letter sent Monday to a group of bipartisan congressional leaders, the academics, led by Columbia Law School’s Christina Ponsa-Kraus, said the Puerto Rico Self-Determination Act, which was introduced by Rep. Nydia Velázquez (D-N.Y.), "disserves its purported goal perpetuating the pernicious myth that [multiple sovereignty] options exist. They do not."

"There are two, and only two, real self-determination options for Puerto Rico: statehood and independence. Yet the Puerto Rico Self-Determination Act defies constitutional reality by calling upon Puerto Ricans to define other non-territorial options. There are no other non-territorial options," reads the letter, which also was signed by professors at Harvard Law School. 

That argument has been strengthened over the past five years, as the Supreme Court decided two major cases that defined Puerto Rico's current status as a territory under the Constitution and closed the door to any status that could offer U.S. territories shared local sovereignty with Congress.

Still, the issue of status has been at the political center of gravity in Puerto Rico since its takeover by the U.S. in the Spanish-American War.

Opponents of statehood, such as Velázquez, had long supported a hybrid sovereignty regime as laid out by the territory's 1952 constitution, which allows some measure of self-rule on the island.

Still, the status debate has been kicked into high gear by the Supreme Court decisions and passage of the Puerto Rico Oversight, Management and Economic Stability Act in 2016.

"As the Court made clear, Puerto Rico is, and always has been, a U.S. territory, and Congress retains plenary power to govern the island under the Territory Clause of the Constitution," the academics wrote.

Velázquez's bill would create a status convention to modify the territory's sovereign status from among a wide range of possibilities, including independence and statehood, but also a range of hybrid statuses whose constitutionality the letter's signatories call into question.

Three South Pacific nations have signed compacts free of association after independence from the United States, giving their citizens certain immigration benefits, but still share certain elements of sovereignty such as defense.

Free association has gained some popularity as a post-independence sovereign option for Puerto Rico, although retention of U.S. citizenship remains a priority for many on the island.

"The U.S. Constitution provides three options for Puerto Rico: statehood, territory or independence. Neither a convention nor act of Congress can change that basic fact. Only a constitutional amendment can do that," said Rep. Darren Soto (D-Fla.), who authored a statehood bill that's also up for consideration in Congress.

The Puerto Rico Statehood Admission Act, introduced by Soto and Puerto Rico Resident Commissioner Jenniffer González-Colón would require Congress to vote whether to admit Puerto Rico as a state and on passage order one final plebiscite of Puerto Rican voters to accept or decline Congress's offer of statehood.

The Soto-González-Colón bill was introduced by Sen. Martin Heinrich (D-N.M.) in the Senate.

Velázquez's bill is also supported by Rep. Alexandria Ocasio Cortez (D-N.Y.) and Sen. Bob Menéndez (D-N.J.), who introduced it in the Senate.

A representative for Velázquez did not immediately return a request for comment on the letter.

Senate Minority Leader Mitch McConnell (R-Ky.) and House Minority Leader Kevin McCarthy (R-Calif.) did not respond to a request for comment.

Democratic leaders have avoided taking sides in the fight, as supporters of the two bills whip support for either side behind the scenes.

Even as Speaker Nancy Pelosi (D-Calif.) and Senate Majority Leader Sen. Charles Schumer (D-N.Y.) have stayed out of the fray, perceptions of support for either side have brought criticism.

Soto last month singled out Schumer for "trying to appease politics at home" after the Senate leader made comments that were perceived to be in favor of Velázquez's bill.

Many Democrats, including Schumer and President Biden, have in the past spoken in favor of statehood, only to backtrack later as a nod to progressives, who generally support more sovereignty for the island rather than permanent union with the United States.

"In the 123 years since the United States annexed Puerto Rico, Congress has never offered Puerto Ricans the choice to become a state. Instead, the United States has allowed Puerto Rico to languish indefinitely as a U.S. territory, subjecting its residents to U.S. laws while denying them voting representation in the government that makes those laws," wrote the academics.