The general counsel of the Defense Department, Jeh Johnson, wrote in a letter transmitted to the author that he had signed two nondisclosure agreements with the Navy in 2007 that obliged him to "never divulge" classified information.
"This commitment remains in force even after you left the active duty Navy," Johnson wrote. He said the author, Matt Bissonnette, left active duty "on or about April 20, 2012," which was nearly one year after the May 2011 raid.
By signing the agreements, Bissonnette acknowledged his awareness, Johnson wrote, that "disclosure of classified information constitutes a violation of federal criminal law." He said it also obliged the author to submit his manuscript for a security review by the government before it was published. The Pentagon has said the manuscript was not submitted for review, although it obtained a copy last week.
Johnson said that after reviewing a copy of the book, "No Easy Day," the Pentagon concluded that the author is in "material breach and violation" of the agreements.
The book is to be published next week by Penguin Group (USA)'s Dutton imprint. The Associated Press purchased a copy Tuesday.
Johnson addressed his letter to Mr. "Mark Owen," using quotation marks to signify that that this is the author's pseudonym. His real name is Matt Bissonnette.
Bissonnette referred requests for comment about the letter to his publisher, which was not immediately available.
"I write to formally advise you of your material breach and violation of your agreements, and to inform you that the department is considering pursuing against you, and all those acting in concert with you, all remedies legally available to us in light of this situation," Johnson wrote.
The Pentagon has not revealed how it got a copy of the book.
Johnson noted that "copies of the book have apparently already been released." He added, "further public dissemination of your book will aggravate your breach and violation of your agreements."
The Pentagon did not release copies of the nondisclosure agreements that it said Bissonnette had signed in 2007. A spokesman, Army Col. Steve Warren, said they were being withheld because they include the author's real name and his signature.
In his book, Bissonnette wrote that the SEALs spotted bin Laden at the top of a darkened hallway and shot him in the head even though they could not tell whether he was armed. Administration officials have described the SEALs shooting bin Laden only after he ducked back into a bedroom because they assumed he might be reaching for a weapon.
Military experts said Wednesday that if Bissonnette's recollection is accurate, the SEALS made the right call to open fire on the terrorist mastermind, who had plenty of time to reach for a weapon or explosives as they made their way up to the third level of the house where he hid.