The D.C. Circuit's 113-pages of non-opinion this week, in which it declined to rehear en banc an earlier panel decision in the Al Bihani case, warrants reflection at a number of levels. I will leave for Jack Goldsmith the very rich subject of the judges' competing opinions on the relationship between international law and the AUMF--opinions for which Jack's (and Curtis Bradley's) academic work is perhaps the principal source. I wish to focus on a different aspect of the opinion, an aspect that involves some of Bobby Chesney's and my work. Back in January, Bobby and I (along with a former Brookings colleague named Rabea Benhalim) released a report on the law emerging from the Guantanamo habeas cases. The report, which we are currently updating, is lengthy and multi-faceted, but its basic point was that the law of detention coming out of the post-Boumediene habeas cases is a muddle. The judges who are hearing these cases, we argued, have disagreed about a great many issues that are foundational to the procedural and substantive law of detention. This point is, well, a matter of simple fact; it should not be subject to dispute among serious people. And yet, to our surprise, it has been disputed. The report's critics have contended that, in fact, a coherent law of detention is emerging from all of these cases. And to whatever extent the lower court judges have disagreed, the D.C. Circuit is happily harmonizing the law. We were, it seems, alarmists. There is more than a grain of truth in the notion that the D.C. Circuit is imposing a degree of uniformity on the lower courts. That's the way the appellate process works. And on some issues--the role of hearsay evidence, for example--the handful of appeals the court has handed down to date have clarified matters considerably. But there's another side to the D.C. Circuit's work, which the Bihani case illustrates: In certain important areas, the appeals court has unsettled matters on which the lower court judges had reached a rough kind of consensus. The first of these areas concerned the burden of proof in these habeas cases--which, if you think about it for a moment, is a rather elemental feature of any legal regime. All of the district judges had agreed that the government bears the burden of proof and that it had to prove its case by a preponderance of the evidence. This year, however, a D.C. Circuit panel threw a wrench into that consensus. It ordered the parties in case called Al Adahi to brief the question of whether the government's burden was really that tough. And even after the government declined to ask for a lower standard, the panel made clear that it believed a lower standard was appropriate. Judge Raymond Randolph, writing for the unanimous panel, wrote baldly that "we doubt . . . that the [Constitution] requires the use of the preponderance standard." In the absence of any dispute between the parties on the question, the panel applied the standard arguendo. But at least as I read it, Al Adahi stands as an invitation to this or some future administration to reopen the question at any time of its choosing. What had been a point of agreement is now a big open question. Then came yesterday's decision. To put it mildly, the question of whether the laws of war--either on their own or incorporated through the AUMF--govern American detention operations or their adjudication had not been roiling the lower court. The judges there all assumed or held that law-of-war principles at some level informs these cases. This simply wasn't a big deal down below. At the D.C. Circuit, by contrast, this question is a very big deal--at least for some of the judges. Judge Brett Kavanaugh cares enough about it to write nearly 90 pages on the subject. Judge Janice Rogers Brown feels strongly enough to blast her colleagues for muddying her earlier opinion (holding that the laws of war do not govern these cases, over which only American statutory law holds sway) and to warn darkly that one of her colleagues, Senior Judge Stephen Williams, in his own opinion "offers a hazy but ominous hermeneutics." (I'm not sure what this means either, but it sure sounds scary, doesn't it?) Once more, the D.C. Circuit has taken a matter not seriously in contest among the district judges and thrown it open. A litigant in the D.C. Circuit, and therefore in the lower court as well, knows now that a law-of-war argument will get him nowhere before a panel including Judge Kavanaugh and Judge Brown, that it may gain traction before Judge Williams, and that the other judges prefer to remain silent on the subject. My point is not that the D.C. Circuit is wrong to open these questions up. They're quite hard. It is not obvious as a doctrinal matter what the burden of proof should be in these cases, nor is it obvious to me whether Judge Kavanaugh or Judge Williams has the better of the argument over international law. (Judge Brown is by far the least persuasive, in my opinion.) My point, rather, is that it is not simply the case that the rules for Guantanamo habeas challenges are coming more clearly into focus as these cases progress. The appeals process brings clarity on some issues, but it also opens up new questions and creates new areas of instability.