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There are two types of actions. Commission and omission. When Obama announced his various executive orders we were focusing on the "commission" aspect. What slipped by was the "omission" part.

In what was dubbed a “makeshift reorganization” in a January 20 USA Today article, employees tasked with reviewing NICS appeals have been “temporarily” reassigned to assist with the considerable increase in background checks. According to the article, this has created a backlog of 7,100 denial appeals.
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Suspending the NICS denial appeal process takes on an even more sinister character when one contemplates the chief gun control measure advocated by the Obama administration. Under a “universal” background check scheme, individuals would be unable to lawfully obtain firearms without subjecting themselves to a NICS check. If such legislation was currently in force, an individual who found themselves erroneously flagged by NICS, no matter how law-abiding, would have no avenue to legally acquire a firearm and no means to challenge their incorrect NICS status, obliterating their ability to exercise their rights in perpetuity, short of judicial intervention.

This is not trivial.

Being flagged by a background check is not uncommon, it happened nearly 91,000 times in 2014. And it isn't even dispositive of the fact that you can't buy a firearm. The FBI's own documents say that being flagged

“indicates the prospective firearms transferee or another individual with a similar name and/or similar descriptive features was matched with either federally prohibiting criteria or state-prohibiting criteria.”

Now imagine the chaos that would ensue if the the alleged "terror" watch list was fed, uncritically, into this system, adding another 700K or so names, many of which are identical to thousands of other people.

The real thing to watch here is whether the "temporary reassignment" of personnel become permanent. There is no logical reason this can't be instituted. From there it is a but a hop-skip-and-jump to simply saying a person does not pass the background check whether they do or not. (My 2009 self just called me a conspiracy theorist) Without an appeal process in place, buying a firearm could become very problematic.