Only about a quarter of the population of the US (latest estimate 298 million as at July 2006) hold valid passports, and most Americans are used to being allowed able to travel to neighbouring countries with just a driver’s license or birth certificate. Things have changed: now Canadian, Mexican and Bermudan air travellers, as well as U.S. citizens flying home from those countries or the Caribbean, must carry their passports to enter the United States. The new rules do not apply to U.S. territories such as Puerto Rico and the U.S. Virgin Islands.

For now, the rules affect only air travellers. Land and sea travellers will not have to show passports until at least January 2008. Air travellers who cannot produce a passport will have the delightful experience of being interviewed by customs agents, who will decide whether to let them into the country.