Accused terror-plotter Khalid Aldawsari will not have access to classified materials detailing how and why he was monitored under the Foreign Intelligence Surveillance Act, a federal judge in Texas ruled earlier this month. Aldawsari had hoped to argue that the evidence against him derived from electronic surveillance and physical searches should be surpressed, either because the surveillance was improperly conducted or because the FISA warrants authorizing it were improperly obtained.

Aldawsari's argument was straightforward: The broad powers available under FISA are only supposed to be used when the government is seeking "foreign intelligence" about an "agent of a foreign power." Since Aldawsari is being accused of acting independently to plan an act of strictly domestic terrorism, only the usual tools available—under more stringent standards—for ordinary criminal investigations should have been available. Judge Sam Cummings rejected this argument following his own review of the classified evidence in closed chambers: Not only did the FBI have probable cause at the time of their investigation to believe Aldawsari was an "agent of a foreign power," the judge found that Aldawsari did in fact meet FISA's definition of an "agent of a foreign power." The mystery is: How?

The natural answer is is the controversial "Lone Wolf" provision, allowing even a totally independent non-citizen who "engages in international terrorism or activities in preparation therefore" to be targeted under FISA as an "agent of a  foreign power." Aldawsari would seem to be a natural.  But there are a few big problems. First and most importantly, the acting head of the Justice Department's National Security Division testified after Aldawsari's indictment that the provision had never been invoked. Second, it would at least be a legally disputable point whether Aldawsari's alleged plot met the definition of international terrorism. Third, it would be unusual and arguably improper for the court to find not just that federal agents had probable cause to believe Aldawsari was engaged in international terrorism, but that he was engaged in international terrorism when this is precisely what the trial is supposed to prove. However damning the evidence, the court is not supposed to commit itself to Aldawsari's guilt at this stage of the process: It would have been enough to rule that investigators had probable cause for this belief.

But if it's not the Lone Wolf provision that qualified Aldawsari for FISA surveillance, what did? All the government's public statements so far have hewed to the line that he acted alone, after all. One possibility is the he was part of some larger terror group, but the government is publicly pretending ignorance about this fact in hopes that the other members will be lulled into a false sense of security, under the mistaken belief that the government never obtained Aldawsari's communications with them. This doesn't seem likely—Aldawsari's accomplices would have to be incredibly stupid for this stratagem to work—but it's possible.

The final  possibility—and perhaps the most probable—is that Aldawsari really was acting alone, and qualifies as an "agent of a foreign power" for reasons completely unrelated to his planned terrorism. Aldawsari was in the United States on a  student visa and his studies were sponsored by a Saudi corporation that goes conspicuously unnamed in all the  court documents surrounding this case even though many other companies are specifically identified. The identify of that company is no mystery, though: Aldawsari noted on his blog, and it has been reported in the press, that the company in question is SABIC, a petrochemicals giant run and substantially owned by the Saudi royal family.  SABIC almost certainly counts as a "foreign power" for FISA purposes, since it is effectively controlled by a foreign state, even if we assume everything the company does is legal and legitimate. Aldawsari would then automatically qualify as an "agent of a foreign power" himself if he were regarded as an "officer or employee" of SABIC.  Since he was  receiving a stipend from the company to pursue studies that would naturally prepare him to work for SABIC, this characterization hardly seems like a stretch.

If this last scenario is correct, however, it ought to at least give us a bit of pause: If the basis for classifying Aldawsari as an agent of a foreign power susceptible to FISA is just that he was one of dozens of SABIC-sponsored students, then that would sound rather like finding a loophole to invoke FISA's broad powers for what was ultimately a straightforward criminal investigation. That's precisely the sort of thing many people worried about when the Patriot Act allowed FISA to be used whenever there was a "significant" foreign intelligence purpose for surveillance. The previous standard had required foreign intelligence—as opposed to ordinary criminal investigation—to be the "primary purpose."

Obviously there's a lot of missing information here: The judge and the government have facts about this case that the rest of us don't, and there may well be a simple explanation for why this was a wholly unobjectionable use of FISA. But it is a reminder that people outside the government ultimately have no idea how  surveillance decisions under FISA are made in practice, and no opportunity to judge whether the standards employed are adequate to a free society under the rule of law.  Nor are we likely to have any idea soon: As Judge Cummings' opinion notes, no court has ever allowed access to these materials—and indeed, only an absurdly tiny fraction of the people subject to FISA surveillance are ever indicted or tried at all. The general citizenry simply has to trust that the government is using these powers in a manner we would accept if it were subject to public scrutiny.