Washington (CNN) -- Sen. Charles Grassley on Thursday asked Attorney General Eric Holder to provide a legal analysis that endorsed the swap of five Taliban figures held at the Guantanamo Bay prison in Cuba for Army Sgt. Bowe Bergdahl.
It was the latest salvo in clashes between Congress and President Barack Obama over what to some lawmakers appears to be the President's tendency to act without consulting Capitol Hill.
Grassley, the top Republican on the Senate Judiciary Committee, said he was rebuffed earlier this year when he asked the Justice Department to release its legal analysis for when the President issues executive orders.
But on Bergdahl, the lone remaining captive from the wars in Iraq and Afghanistan who was released over the weekend, he thinks the department needs to explain itself.
A U.S. official told CNN the Justice Department's Office of Legal Counsel opinion on the Bergdahl matter was verbal and, as typically happens, likely will be issued in the form of a written opinion later.
The department often refuses to release such opinions because they are considered protected under attorney-client privilege and the presidential executive privilege.
Grassley, in his letter to Holder, nonetheless makes his case that while "it is too late for Congress to express its concerns about these transfers in time to prevent them ... this measure of transparency will at least allow the American people to better understand the administration's purported basis for ignoring the legal requirement that Congress be notified in advance, and shed additional light on this controversial decision."
Grassley also said sharing the Justice Department's legal advice may also ensure the President abides by his oath" to carry out the law.
At issue is the administration's decision to ignore a restriction in the current defense policy law, signed by Obama last December, which requires 30-day notice to Congress before transferring terror detainees from Guantanamo Bay.
Obama attached a statement when he signed the law that called the restrictions on transfers an illegal infringement on presidential executive powers and declared the right to ignore them when national security interests required it.
Susan Rice said on CNN's "State of the Union" on Sunday that the Defense Department was given advice by the Justice Department before the swap.
Hints of the legal advice provided to the Pentagon can be found in statements issued in recent days by the White House.
National Security Council spokeswoman Caitlin Hayden said in a statement that the administration's interpretation of the law determined that the 30-day notification requirement "should be construed not to apply to this unique set of circumstances, in which the transfer would secure the release of a captive U.S. soldier, and the secretary of defense, acting on behalf of the President, has determined that providing notice as specified in the statute could endanger the soldier's life."
Hayden's statement said that because the 30-day notice would have required the Pentagon to delay the swap, the notification requirement would interfere with the President's constitutional power to protect Americans abroad and protecting U.S. soldiers.
Hayden added: "Because such interference would significantly alter the balance between Congress and the President, and could even raise constitutional concerns, we believe it is fair to conclude that Congress did not intend that the administration would be barred from taking the action it did in these circumstances."