Republicans are pointing to nuanced legal positions taken by the Obama administration as evidence it may be planning to transfer detainees held at Guantánamo Bay, Cuba, to a prison in Illinois, despite repeated denials by administration and Democratic officials.

The Justice Department announced Tuesday that it was moving forward on the $165 million acquisition of an unused Illinois prison near Thomson for what it said would become a federal correctional facility for high-security inmates, ignoring objections by House appropriators.

Attorney General Eric H. Holder Jr. stressed that the facility would not — and, legally, could not — be used to house terrorist suspects now housed at the Guantánamo Bay detention facility.

“As I have committed publicly — and as I now reiterate — Thomson will not be used to house Guantánamo detainees,” Holder said in a letter to Rep. Frank R. Wolf, R-Va., who chairs the Appropriations subcommittee that oversees federal prison spending. The panel has opposed the Justice Department’s efforts to purchase the Thomson prison amid concerns it would be used to house terrorist suspects, prompting the department to circumvent Congress this week.

“The entire Thomson facility will house only [Bureau of Prisons] federal inmates, and will be operated solely by the bureau,” Holder said in the letter. “As you know, any transfer of Guantánamo detainees to the United States would be prohibited by statute. Thomson represents a solution to the safety needs of the bureau; it is unrelated to the detainees at Guantánamo.”

Republicans, however, are not convinced. They accuse the administration of taking subtle legal positions that are at odds with its public statements and could be designed to lay the groundwork for a future policy shift on detainee transfers to facilities in the United States.

Sen. Charles E. Grassley of Iowa, the top Republican on the Judiciary Committee, pointed to a Justice Department court filing Tuesday that clears the way for the purchase of the Thomson prison. In the filing, the department told a federal district court in Illinois that the prison is being purchased “in order to alleviate crowding of the federal inmate population in that region, as well as to provide humane and secure confinement of individuals held under authority of any act of Congress, and such other persons as in the opinion of the attorney general of the United States are proper subjects for confinement in such institutions.”

“BIG problem if that includes Gitmo detainees,” Grassley tweeted about the court filing.

Laws Prevent Transfer

The transfer of Guantánamo Bay detainees is prohibited under appropriations and defense authorization laws. The fiscal 2012 spending package (PL 112-55) that included spending for Commerce, Justice and science agencies as well as agriculture and transportation programs, for example, prohibited funds from being used for the transfer of detainees from Guantánamo Bay or to “construct, acquire or modify any facility in the United States” for that purpose.

In addition, Sen. Richard J. Durbin, D-Ill., told a Chicago newspaper Tuesday that international treaties also prohibit the transfer of those detainees to the Thomson prison.

“This argument they can move Guantánamo detainees in the future there is completely false for the following reason: We’ve signed these treaties with countries around the world, and one of them is you don’t put military prisoners in anything other than a military prison,” Durbin said.

Christina Mulka, a Durbin spokeswoman, said Wednesday, “It is Sen. Durbin’s understanding that the Defense Department and State Department take the position that the Geneva Conventions, as well as the law of war, require enemy combatants to be held in military detention, separated from prisoners who have been convicted of crimes.”

But Wolf and other Republicans question whether the administration is committed to the laws that are on the books or whether, in the future, it may try to circumvent or change them. Wolf noted in a July letter to Holder that the administration “has not rescinded or renounced” executive orders related to the closure of the military prison in Guantánamo Bay, and that one such order includes language allowing transfers from Guantánamo to “another United States detention facility.”

In the same letter, Wolf noted that the White House issued a Statement of Administration Policy on May 15 regarding the fiscal 2013 defense authorization bill (HR 4310) that opposed congressional language restricting detainee transfers to the United States.

In the statement, the Office of Management and Budget objected to provisions that “unnecessarily renew, supplement, or enhance the restrictions on the transfer of Guantánamo detainees into the United States or a foreign country. The administration continues to strongly oppose these provisions, which intrude upon the executive branch’s ability to carry out its military, national security and foreign relations activities and to determine when and where to prosecute Guantánamo detainees.”

House Republicans have repeatedly questioned the Justice Department’s credibility and the timing of the department’s move to purchase the Thomson prison — coming during a congressional recess, with the House unable to block it — as “too fishy to ignore,” said the House GOP aide.