All civilizations fall. That's what "they" say, and who can argue? Even from the vantage point of the American Superpower, the historic record -- from Greece to Rome, from Mongols to Moguls, from the Age of Spain to Pax Britannica -- looks less than encouraging, particularly when you consider society's nasty self-destructive streak.

But if the end is clear -- let's hope it's not near -- the causes will drive historians of the future crazy. I can hear them now: "They had unprecedented freedom. They had massive nukes. They had great lawns and a thousand different kinds of potato chips. What went wrong?" Solving the riddle won't be easy. But some day, when historians wonder about the decline and fall of, well, us, I hope they examine Super Bowl XLI in the year 2007. It marked a crucial turning point.

How can that be? Nothing happened on the field or on screen to cause our sunken but stable culture of idolized thuggishness, bad pop stars and crude commercialism to spin out of control and plummet to the ground. There wasn't a wardrobe malfunction in sight. What historians will need to examine instead is something that didn't materialize on game day.

That something is a recruitment ad for the U.S. Border Patrol that the National Football League refused to print in-game programs distributed at the stadium and over the Internet because it was "controversial."

There is a hefty chunk of symbolism to ponder here, beginning with the staggering concept that a recruitment effort on behalf of the U.S. Border Patrol can be considered "controversial" by any American organization. More alarming still is that the organization here is professional football, hobbyhorse to redmeat America, the kind of people -- the kind of men -- who are stereotypically supposed to have retained their atavistic reflexes when it comes to defending hearth and home.

The Border Patrol ad in question lists an agent's prospective duties in protecting that last line of defense for the United States -- our border. By any measure, this is an affirmative mission that should have a salutary effect on any civilization with even halfway healthy reflexes. The first duty listed in the ad is to "prevent the entry of terrorists and their weapons into the United States." Next, to "help detect and prevent the unlawful entry of undocumented aliens ... and apprehend violators of our immigration laws." And finally, to "play a role in stopping drug smuggling along our borders." This is controversial? The answer is yes, if the NFL is talking. As NFL spokesman Greg Aiello put it to The Washington Times, "The ad that the department submitted was specific to Border Patrol, and it mentioned terrorism. We were not comfortable with that."

Tsk, tsk. Isn't that just too bad. But is the NFL really saying it isn't "comfortable" with supporting government efforts to prevent terrorism at the border?

Aiello went on. "The borders, the immigration debate is a very controversial issue, and we were sensitive to any perception we were injecting ourselves into that." The key phrase here is sensitive to "any perception." It becomes clear that the NFL is not focused on the American perception.

The fact is, the ad wasn't "injecting" anything into the immigration debate. The ad's substance concerned not, for example, the pros and cons of "guest worker" programs, but defending the border and upholding the law. And who could be "sensitive" about that? All I can think of, besides terrorists and drug smugglers, is illegal aliens and their families back home. Considering that the NFL hopes to add a Mexican franchise to its roster, maybe Mexico is where the NFL thinks discomfort and sensitivity over "the borders" come from. Which isn't exactly going to win a trophy for being all-American.

But maybe there's more than a supranational business decision to consider. The NFL has revealed something new about the state of the border in the popular imagination. Even as one large constituency of the country wants to mark our southern border with a fence, making it more tangible, another wants to make the border more elastic, making it less meaningful, even less defensible. This political struggle has had the effect of making the border itself controversial, a development the NFL was somehow mindful of in its decision to rebuff the border agency.

Next question: When a nation's border becomes controversial, how long does its sovereignty last? And what happens to the civilization? All of which is precisely why future historians of American decline shouldn't overlook what didn't happen at Super Bowl XLI.