Beyond these case law references, there are no details of how this “primary methodology” of shielding classified programs integrates into DEA investigations.

The remaining three methods help to flesh out what the mystery tactic is somewhat, if only by differentiation. The second method leverages provisions in the Classified Information Procedures Act (CIPA) to limit the introduction of classified intelligence as evidence, or its release to the defense in discovery. Under CIPA, a judge may review classified information to determine its relevance to the case before the trial begins. If the judge deems the information relevant, CIPA allows the government to provide the defense with redacted materials or unclassified substitutes that would not divulge sensitive sources or intelligence collection methods.

The third method invokes the Foreign Intelligence Surveillance Act (FISA). While the DEA did not redact references to FISA as it did with the first method, all operational details have been withheld. The fourth acceptable method reviewed in the training module is parallel construction, as first uncovered by Reuters last August.

But the first and apparently most broadly used of these tactics remains a secret. I have requested a Vaughn index for the parallel construction request to better understand the redactions invoked. Until additional details come to light, the American public that the DEA claims would accept this hushed method remains approvingly uninformed.

Shawn Musgrave is the projects editor at MuckRock , a news organization that specializes in government transparency and allows users to submit their own Freedom of Information Act requests.