The counterterror expert I spoke to who offered the most unequivocal support for enhanced security at the site was Kip Hawley, a former head of the Transportation Security Administration. Hawley saw both threat-based and emotional justifications for heightened security. But even he would not enter into a discussion on the effectiveness of the specific measures at the memorial. Neither would a Sept. 11 memorial representative, except to say that the security protocols are appropriate for the twice-targeted WTC site.

Again, for the sake of argument, let’s assume there is a risk and that the Sept. 11 memorial’s security regime effectively lowers it. Then it’s worth it, right?

Maybe not even then. I suggested to Schneier that although the security measures wouldn’t stop a coordinated attack by al-Qaida, they might deter a lone actor. He agreed but noted that the security measures wouldn’t stop that lone unsophisticated actor — they’d only shift the location of his attack. In terms of lives lost, if not symbolism, an attack would be just as bad “in a million places,” said Schneier. In many — a crowded mall or train — it might be much worse.

But doesn’t the 9/11 site deserve special protection? That’s essentially the view of experts who supported enhanced security simply because the site is so iconic. Schneier calls that an emotional argument “which will cost lives, rather than save them, if the money could be better spent elsewhere.” Schneier’s approach doesn’t account for the emotional weight of the 9/11 site. And who knows — presumably there’s plenty of “smart” security, too, behind the scenes. But his point — that every dollar we spend on security theater is a dollar we don’t invest in smarter security — gets harder to ignore each time your memorial ticket is checked, scanned, or drawn on with the blue pen.

Why else might the Sept. 11 memorial’s security not be worthwhile? Because it makes the site less open and accessible. Bizarrely, the Web page that lists the memorial’s limited hours (10 a.m. until 6 or 8 p.m., depending on the season) also describes the memorial as a place “meant to be experienced at all times of the day.” I asked Barrett if he could think of any similarly restricted locations; he suggested hotels in Kabul and Islamabad.

In terms of balancing America’s most cherished values, no other American memorial marking a terrorist act has struck anything like the “balance” New York has. The Oklahoma City memorial, the Flight 93 memorial, even the Sept. 11 memorial at the Pentagon: None require advance names, photo ID or airport-style security, let alone all three. The outdoor Oklahoma City memorial — open 24/7 year-round — seems more concerned with helping visitors find nearby doggie daycare than burdening them with byzantine rules and regulations. Abroad, access to highly urban memorials in freedom-loving countries better acquainted with terrorism — Spain, the United Kingdom — is unfettered. Neither the memorial to the London July 7, 2005, attacks nor the Madrid station bombing memorial require preregistration, ID, or security checks.

The Sept. 11 memorial’s security is perfect in at least one inadvertent sense: There’s no better place to consider our national reaction to 9/11 than at the memorial, and its security regimen inspires us to do just that. Indeed, much of the memorial experience — the ID requirements, long lines, senselessly repetitive checks of home-printed documents, restrictions on personal belongings, agents snapping between diligence, boredom, and aggression — recalls nothing so much as post-9/11 air travel.