TSATSALast week I expressed the hope that I would be allowed to take my Leatherman Juice S2, which has a six-centimeter blade, onto airplanes after the Transportation Security Administration's new policy regarding prohibited items takes effect on April 25. But it turns out that the TSA's definition of blade (see illustration) includes the unsharpened metal beneath the edge, which would make the knife on my Leatherman one centimeter too long. (The width, by contrast, is well under the half-inch maximum.) But are TSA agents really going to be measuring knives? According to CBS News, the TSA "argues the change will speed up security lines." Not if it requires agents to break out their rulers and invites disputes about exactly how long and wide a knife blade is.

Flight attendants and pilots have a different concern, noting that the newly permitted knives are just as dangerous as the still-forbidden box cutters. Members of Congress such as Sen. Charles Schumer (D-N.Y.) and Rep. Peter King (R-N.Y.) are worried too. Rep. Edward Markey (D-Mass.) plans to introduce a No Knives Act that would block the policy change. "On 9/11," he says, "we learned that in the confines of an airline cabin, even a small knife can lead to devastating consequences."

The critics have a point. The distinction between box cutters and pocket knives is emotional and aesthetic rather than logical or practical. Because the 9/11 hijackers happen to have used that particular implement, it is forever banned from airplane cabins, even though it is not really any more threatening than the tools that the TSA wants to allow. But TSA Administrator John Pistole argues that small knives do not pose much of a risk in light of reinforced cockpit doors and other post-9/11 security measures. He wants his agents to focus on potentially catastrophic threats—"primarily nonmetallic explosive devices, the bombs that can bring down an aircraft"—rather than confiscating pocket tools.

Enforcing the restrictions on knife length and width, of course, could be pretty distracting too, depending on how persnickety the TSA is. The TSA is perfectly capable of combining persnicketiness with ineptitude: Although I have lost several pocket knives over the years because I forgot to leave them at home or put them in checked baggage, I have also accidentally carried them onto airplanes without anyone noticing, so the ban on knives clearly never meant that airplane cabins were knife-free zones. Furthermore, Pistole's fear of nonmetallic explosives is the rationale for confiscating water bottles and otherwise policing liquids and gels, which has to rank high in terms of inconvenience and pointlessness.

Pistole nevertheless deserves credit for his willingness to revisit policies that never made much sense, thereby risking the wrath of alarmist micromanagers like Schumer and Markey. Maybe one day we will even be able to keep our shoes on at the airport.

[Thanks to Robert Woolley for the tip.]