BORDERLINE

These changes reflected a severe and acute new asymmetry: Borders became harder for governments to control, and easier and more lucrative for violators to bypass. Anyone seeking to cross them found it easier to do so, while government agencies floundered in their efforts to regulate the new world they had helped create.

Today's borders are violated, enforced and remade not only on the ground but also in cyberspace, multilateral agencies and the virtual world of international finance.

Consider the most mundane of examples: the ATM machine. When an immigrant living in the United States sends her ATM card to her children in the Philippines and they draw money from her U.S. checking account, where has the transaction taken place? Did the kids cross a border to tap the funds from an American bank? In a sense, they did -- the ubiquitous ATM has become a powerful, easy-to-use, border-crossing tool. Often, such crossings are perfectly legal. But not always.

National boundaries are also being transformed by new -- or newly empowered -- international institutions. For example, when the World Trade Organization's 149 member states agree on the reduction of tariff rates around the globe, our time-honored beliefs about controlling sovereign borders are upended. On trade, the borders that matter may be drawn at the WTO headquarters in Geneva as much as anywhere else.

The fluid, unpredictable nature of modern borders is evident even among the most geographically isolated and remote nations on earth. Try landlocked Bolivia and Afghanistan. Their rugged geography and poor roads make internal travel exceedingly difficult and time-consuming. Yet narco-traffickers regularly and swiftly connect Bolivia's remote Chapare region, where coca is cultivated, with Miami or New York, where cocaine is consumed (with a processing stopover in the jungles of Colombia and a transshipment detour to a deserted beach in Haiti). And in Afghanistan, opium traffickers seamlessly link the Deshu district in the lawless Helmand province with elegant consumers in London or Milan.

Even for experienced travelers, reaching Chapare or Deshu is a tough proposition. But location and geography now matter less and less for traffickers or for anyone seeking to violate national borders. In major cities across the globe, the availability of banned merchandise stands as a monument of sorts to nations' eroding sovereignty -- no matter the billions of dollars that governments spend seeking to keep such goods from reaching their shores and penetrating their borders.

In 2004, the Guardian published a dispatch from the banks of the Yalu River, on the border between China and North Korea. "Here and there shadowy figures can be seen on both sides of the misty river quietly carrying out an illegal -- but thriving -- trade in women, endangered species, food and consumer appliances," wrote Jonathan Watts.

If a paranoid police state such as North Korea is incapable of controlling its borders and deterring illicit trade, there seems to be little hope for open, democratic and technologically advanced nations seeking to uphold their sovereign borders. This issue gained urgency in the United States in particular after the terrorist attacks of Sept. 11, 2001, when security concerns became paramount.

Yet the paradox of policing borders in a high-tech, globally integrated era is that today, less sovereignty may equal more protection. In order to reinforce national boundaries and combat terrorism, one of the most effective tools a government can deploy is collaboration with other nations -- in effect, ceding or "pooling" certain aspects of their sovereignty.

That is no easy task. It requires partnering with less efficient, less democratic and less trustworthy nations and sharing information, technology, intelligence and decision-making power. In many quarters -- Washington and beyond -- the notion of diluting national sovereignty verges on treason.

But if sovereignty is indeed a hallowed concept, it has become a somewhat hollow one, too. Traditional borders are violated daily by countless means, and virtual borders seem even more permeable and misunderstood. "Closing the border" may appeal to nationalist sentiments and to the human instinct of building moats and walls for protection. But when threats travel via fiber optics or inside migrating birds, and when finding ways to move illegal goods across borders promises unimaginable wealth or the only chance of a decent life, unilateral security measures have the unfortunate whiff of a Maginot line.

mnaim@carnegieendowment.org

Moisés Naím is the editor of Foreign Policy magazine and author of "Illicit: How Smugglers, Traffickers, and Copycats are Hijacking the Global Economy" (Doubleday).