The New York Times’s Charlie Savage reports that the FBI is preparing to release a new Domestic Investigations and Operations Guide (DIOG), further relaxing the rules governing the Bureau’s investigation of Americans who are not suspected of any wrongdoing.

This comes just three years after the last major revision of FBI manual, which empowered agents to employ a broad range of investigative techniques in exploratory “assessments” of citizens or domestic groups, even in the absence of allegations or evidence of wrongdoing, which are needed to open an “investigation.” The FBI assured Congress that it would conduct intensive training, and test agents to ensure that they understood the limits of the new authority—but the Inspector General found irregularities suggestive of widespread cheating on those tests.

Agents can already do quite a bit even without opening an “assessment”: They can consult the government’s own massive (and ever-growing) databases, or search the public Internet for “open source” intelligence. If, however, they want to start digging through state and local law enforcement records, or plumb the vast quantities of information held by commercial data aggregators like LexisNexis or Acxiom, they currently do have to open an assessment. Again, that doesn’t mean they’ve got to have evidence—or even an allegation—that their target is doing anything illegal, but it does mean they’ve got to create a paper trail and identify a legitimate purpose for their inquiries. That’s not much of a limitation, to be sure, but it does provide a strong deterrent to casual misuse of those databases for personal reasons. That paper trail means an agent who might be tempted to use government resources for personal ends—to check up on an ex or a new neighbor—has good reason to think twice.

Removing that check means there will be a lot more digging around in databases without any formal record of why. Even though most of those searches will be legitimate, that makes the abuses more likely to get lost in the crowd. Indeed, a series of reports by the Inspector General’s Office finding “widespread and serious misuse” of National Security Letters, noted that lax recordkeeping made it extremely difficult to accurately gauge the seriousness of the abuses or their true extent—and, of course, to hold the responsible parties accountable. Moreover, the most recent of those reports strongly suggests that agents engaged in illegal use of so-called “exigent letters” resisted the introduction of new records systems precisely because they knew (or at least suspected) their methods weren’t quite kosher.

The new rules will also permit agents to rifle through a person’s garbage when conducting an “assessment” of someone they’d like to recruit as an informant or mole. The reason, according to the Times, is that “they want the ability to use information found in a subject’s trash to put pressure on that person to assist the government in the investigation of others.” Not keen into being dragooned into FBI service? Hope you don’t have anything embarrassing in your dumpster! Physical surveillance squads can only be assigned to a target once, for a limited time, in the course of an assessment under the current rules—that limit, too, falls by the wayside in the revised DIOG.

The Bureau characterizes the latest round of changes as “tweaks” to the most recent revisions. That probably understates the significance of some of the changes, but one reason it’s worrying to see another bundle of revisions so soon after the last overhaul is precisely that it’s awfully easy to slip a big aggregate change under the radar by breaking it up into a series of “tweaks.”

We’ve seen such a move already with respect to National Security Letters, which enable access to a wide array of sensitive financial, phone, and Internet records without a court order—as long as the information is deemed relevant to an “authorized investigation.” When Congress massively expanded the scope of these tools under the USA Patriot Act, legislators understood that to mean full investigations, which must be based on “specific facts” suggesting that a crime is being committed or that a threat to national security exists. Just two years later, the Attorney General’s guidelines were quietly changed to permit the use of NSLs during “preliminary” investigations, which need not meet that standard. Soon, more than half of the NSLs issued each year were used for such preliminary inquiries (though they aren’t available for mere “assessments”… yet).

The FBI, of course, prefers to emphasize all the restrictions that remain in place. We’ll probably have to wait a year or two to see which of those get “tweaked” away next.