(CNN) A federal judge threw a wrench Monday in the Justice Department investigation into potential mishandling of documents from former President Donald Trump's White House by granting his request for a special master to review evidence seized from his Florida home last month.
The win for Trump temporarily prevents the Justice Department's investigative team from accessing the thousands of documents -- some of which are marked as classified -- taken from Mar-a-Lago.
US District Judge Aileen Cannon cleared the way for a third-party attorney to review all the seized materials, not just for documents covered by attorney-client privilege -- the circumstance in which special masters are usually used -- but also for potential executive privilege concerns, a move the Justice Department has said would be "unprecedented."
She did not agree, however, with Trump's arguments that there had been a "callous disregard" for his constitutional rights with the search.
Here are takeaways from the judge's ruling and what happens next:
The primary takeaway is simple: The ruling is a major legal win for Trump.
Trump filed a lawsuit seeking a special master to review the materials the FBI seized last month, and now one will be appointed with the potential to decide that certain materials are out of bounds to the FBI's investigation.
Cannon bought into the skepticism Trump's lawyers raised about the unprecedented search of the Florida resort, as they questioned whether investigators could be trusted to properly filter through the thousands of documents that were seized. The judge rejected the Justice Department's assurances that its internal filter team had already sorted out materials that could be subject to attorney-client privileges.
Ultimately, the special master appointment may merely lead to a delay in the federal investigation into documents taken to Mar-a-Lago, but it now introduces a new layer of uncertainty and unpredictability into the investigation.
The former President did not get absolutely everything he asked for -- the judge did not rule that any materials seized from his home should be returned to him, for instance.
Cannon left undecided many key questions about how the special master will operate. She sketched out a plan for how things will move forward for at least the rest of this week and focused on settling those logistical matters.
She ordered Trump's lawyers and prosecutors to "confer" on several big-ticket items: Who are the proposed candidates to serve as special master? What will their specific "duties and limitations" be? What should be their schedule and pacing? And how much will they be paid for their work?
Both sides were told to file a "joint filing" by Friday, spelling out their answers to these questions. Based on how the case has progressed so far, it seems unlikely that the two sides will agree on much. They'll both be able to put in writing their ideas for how they want this to move forward.
Cannon said she will "expeditiously" issue a court order setting out "the exact details and mechanics of this (special master) review process" after the joint filing comes in.
She noted the need to settle disputes between the parties about "whether certain seized documents constitute personal or presidential records" and "whether certain seized personal effects have evidentiary value."
Trump had said that a special master review needed to go beyond documents covered by attorney-client privilege, and that materials covered by executive privilege should be filtered out as well.
Executive privilege refers to private communications presidents have with their advisers and other types of internal communications within the executive branch that are withheld from public release. While disputes over the privilege have come up in congressional investigations, the reaches of executive privilege -- particularly when a former president is arguing it should apply when a current president is declining to assert it -- is an unsettled area of law.
Cannon's order requires the special master to examine the documents based on "executive privilege" concerns, making the job more expansive than the attorney-client privilege review that happens typically when a special master is appointed. (Documents potentially covered by attorney-client privilege will be part of this special master's review as well, according to Cannon's order.)
She did not elaborate on the parameters the special master should be considering.
In her ruling, Cannon said that the Supreme Court had not ruled out "the possibility of a former President overcoming an incumbent President on executive privilege matters." She quoted from a 1977 Supreme Court case concerning documents from President Richard Nixon's White House, as well as from a Supreme Court order earlier this year that allowed the release of Trump White House documents to House January 6 investigators.
Cannon quoted the Supreme Court saying in the recent case that the questions are "unprecedented and raise serious and substantial concerns" when it comes to scenarios where a former president is claiming to assert executive privilege over materials for which that privilege has been waived by the incumbent.
She also drew from a separate statement from Justice Brett Kavanaugh in that case in which Kavanaugh said it would "eviscerate the executive privilege for Presidential communications" if courts were to conclude that a former president could not "invoke the Presidential communications privilege for communications that occurred during his Presidency, even if the current President does not support the privilege claim."
Cannon conceded that, when all is said and done, Trump's assertions of executive privilege might fail, but she said that "does not negate a former President's ability to raise the privilege as an initial matter."
The judge is not stopping the US intelligence community's from continuing to examine the documents as part of its damage assessment into the potential risk to national security.
Director of National Intelligence Avril Haines told Congress last month that the intelligence community would be conducting an assessment "of the potential risk to national security that would result from the disclosure of the relevant documents." The intelligence community has also been working with the FBI since mid-May to examine some of the documents taken from Mar-a-Lago, CNN previously reported.
While the FBI investigation is related to at least three potential crimes -- violations of the Espionage Act, obstruction of justice and criminal handling of government records -- the intelligence review is primarily concerned with determining whether the disclosure of the material that was housed at Trump's resort and residence could place sensitive intelligence sources at risk.
The judge repeatedly pointed to the "extraordinary circumstances" present in the special master dispute, given that it involved the "unprecedented" search of a former president's home. She also said there was a risk of "stigma" that would come with a prosecution that was brought wrongfully and said that the threat was greater in this scenario because Trump is a former president.
"As a function of Plaintiff's former position as President of the United States, the stigma associated with the subject seizure is in a league of its own," she wrote. "A future indictment, based to any degree on property that ought to be returned, would result in reputational harm of a decidedly different order of magnitude."
There were other examples in the order of Cannon putting Trump, as a former president, in a special class of defendants. She said that Trump's reliance on "cooperation between former and incumbent administrations regarding" the exchange of documents also cut in favor of her intervening. (The Justice Department has pointed to several examples in the litigation of Trump's team slow-walking that negotiation).
In a footnote rebutting the DOJ's arguments that special masters are usually appointed to review searches of an attorneys' offices, Cannon wrote that she did "not see why these concerns would not apply, at least to a considerable degree, to the office and home of a former president."
The ruling does not shut down the Justice Department's criminal investigation. Trump still has potential legal jeopardy. But the ruling will limit what investigators can do, and may slow things down a bit, while the special master review is underway.
A Justice Department spokesman said Monday that officials are "examining the opinion" and considering "appropriate next steps." The one-sentence statement did not explicitly reference an appeal, though that is the obvious next possible option for prosecutors.
If prosecutors appeal, those proceedings would be handled by the 11th US Circuit Court of Appeals, which is based in Atlanta. The court has four full-time judges appointed by Democratic presidents, and seven by Republican presidents, including six by Trump.
A three-judge panel would be randomly selected to hear the appeal. Whichever side loses that round would get an opportunity to ask the entire 11-member court to rehear the appeal "en banc." The losing side also could appeal to the Supreme Court, which has a conservative majority.
DOJ officials might choose to only appeal a portion of Cannon's multi-pronged ruling.
Andrew Weissmann -- a venerated ex-DOJ official, former Robert Mueller team prosecutor and prominent Trump critic -- tweeted that the Justice Department should "appeal immediately" the part of the ruling that blocks investigators from doing anything with the seized materials, which he called "precedent that is too wrong to not appeal."
Federal judges routinely handle matters that involve the president who put them on the bench. The fact that Cannon was appointed by Trump, and that Trump filed this lawsuit, is not grounds for Cannon to recuse herself from the case, though she could if she thinks it creates a perception of unfairness.
For his part, Trump has a history of politicizing the judicial branch, by attacking "Obama judges" and openly saying that he expects his appointees to do his legal bidding. But this twisted view toward judicial loyalty seems to be pretty one-sided, with Trump expecting political fealty while most judges try to ignore his out-of-court rhetoric and focus on the facts.
A question lingering over this and other investigations that touch on the former president is how the Justice Department will view the so-called "60-day rule" as applying to investigations connected to Trump.
The "rule" is an internal DOJ policy that discourages public investigative steps that could influence an election 60 days before Election Day. Trump's allies have argued the department's Trump documents investigation stands to run afoul of this principle, even though Trump himself is not a candidate.
It's not clear if DOJ was calibrating its approach to the documents probe with that rule in mind, and if prosecutors are doing so, it's also not clear whether the appointment of a special master affects those plans.
The investigation appears to be in its very early stages. Prosecutors have described it as such in public court proceedings. And the types of attorneys publicly involved in the probe -- mainly coming from the DOJ's National Security Division -- also suggest the probe is at an early phase, former agency officials have said.