Given Donald Trump's continuing fondness for Twitter over the course of his rise to power, it was perhaps inevitable that sooner or later, we would start seeing his tweets showing up in litigations. Turns out it happened sooner, in fact before he even took office. In the weeks before the inauguration, counsel in Guantanamo habeas cases filed what appear to be the first motion referring, implicitly, to Trump's tweets—at least the first that we're aware of in the national security context.
On January 13th, counsel for Soufyan Barhoumi and Abdullatif Nasser filed an emergency motion for the detainees' release from Guantanamo Bay. Barhoumi, an Algerian detainee who has been held at Guantanamo since 2002, was cleared for transfer to his home country by a Periodic Review Board in August but had yet to receive the necessary certification from the Secretary of Defense approving his release. Nasser was also cleared by the Periodic Review Board for transfer to his native Morocco and awaiting the Secretary's approval.
Under the NDAA, the Secretary of Defense's certifications must be provided to Congress 30 days in advance of any detainee transfer, with one exception: a transfer may go forward without the 30-day waiting period if it takes place pursuant to a court order.
According to counsel for Barhoumi and Nasser, the 30-day period presented a serious problem for their clients' prospects of release. Even if now-ex-Defense Secretary Ash Carter had signed the paperwork right on the 13th, it would take until February 11th for Barhoumi and Nasser to be transferred—at which point the Trump administration would be firmly in place. In Nasser's case, the government of Morocco only provided the United States with the proper security assurances regarding Nasser's transfer on December 28th, so the earliest that Nasser could possibly have been released would have been January 26th, a week into the new administration.
...absent a judicial order effecting release, Petitioner will suffer substantial prejudice because the incoming administration intends to end all transfers immediately. He will, in the estimation of all parties, become a victim of the calendar. The certification-and-notice requirement will have cost Petitioner his chance at freedom—a chance which, as is uncontested by the government, may not recur for four or more years. In that regard his detention will be classically arbitrary, perpetual, and unlawful (emphasis added).
As such, the emergency motion requested that the U.S. District Court in Washington order Barhoumi's release to get around the 30-day notice period and allow him to be transferred prior to Trump's inauguration.
On January 12, however—the day before the emergency motion was filed, but according to Barhoumi's counsel, "two days after Petitioner first sought consent to the relief sought in this emergency motion from counsel for the government"—Secretary Carter determined not to approve Barhoumi's transfer. On these grounds, among others, Judge Rosemary Collyer denied the motion for Barhoumi's release on January 18th.
Because of Morocco's tardiness in providing security assurances, Nasser's case is somewhat different. In a response to the emergency motion, the government argued that the late date at which it received Morocco's assurances led Secretary Carter to "elect to leave that decision [on Nasser's release] to his successor," Secretary of Defense James Mattis, because of the 30-day notice requirement. In the view of Nasser's counsel, the distinction between Nasser's case (in which the Secretary of Defense reached no determination) and Barhoumi's case (in which the Secretary affirmatively rejected Barhoumi's release) was sufficient as to merit a court order for Nasser's release. However, Judge Colleen Kollar-Kotelly denied that motion too, citing Judge Collyer's earlier ruling.
So this tweet appears to have generated no adverse litigation consequences for the United States. But the mini-flap is probably a sign of things to come, particularly now that the @realDonaldTrump account speaks for the executive branch of the United States.
The emergency motion, Barhoumi's reply brief, the government's response and Nasser's reply in Nasser's case, and the rulings from both Judge Collyer and Judge Kollar-Kotelly are included below.