News reports from Britain indicate that three Islamist leaders in that country – Omar Bakri Mohammed, Abu Uzair, and Abu Izzadeen – could face treason charges.

The first two of them said, after the July 7 attacks in London, that they would not warn the police if they knew of plans to carry out another bomb attack in Britain. The third praised the London bombings for making the British"wake up and smell the coffee."

But are treason charges realistic? Not terribly, For starters, Mr. Mohammed has fled and some Islamists are not British citizens. For another, as an official, Lord Carlile, pointed out, there is probably not"a lawyer still alive and working who has ever appeared in any part of a treason case." Indeed, Britain has seen no application of the Treason Act - originally passed in 1351 - since 1966, except for two minor instances.

This absence points to a deeper reality: the crime of treason is now as defunct as blue laws, prohibition of alcohol, or laws banning miscegenation. I predict that, short of radical changes, no Western state will again prosecute its citizens for treason.

Until recently treason was a powerful concept. The U.S. Constitution defines it as"levying war against [the United States], or in adhering to [its] enemies, giving them aid and comfort." Famous traitors in history include Benedict Arnold, Vidkun Quisling, and Lord Haw-Haw.

The law of treason was always difficult to apply but now it is impossible, as illustrated by the case of the American Talib, John Walker Lindh. Captured on a battlefield in Afghanistan bearing arms against his countrymen, treason charges clearly applied to him. But he was charged with lesser offences and pled guilty to even more minor ones such as"supplying services to the Taliban."

Why this collapse? Because the notion of loyalty has fundamentally changed. Traditionally, a person was assumed faithful to his natal community. A Spaniard or Swede was loyal to his monarch, a Frenchman to his republic, an American to his constitution.

That assumption is now obsolete, replaced by a loyalty to one's political community – socialism, liberalism, conservatism, or Islamism, to name some options. Geographical and social ties matter much less than of old.

The Boer War of 1899-1902 marked an initial milestone in this evolution, when an important segment of the British public vocally opposed its government's war arguments and actions. For the first time, a faction dubbed"Little Englanders" openly defied the authorities and called for ending the war effort.

Another bellwether came during World War I, when the incompetence of the Allied military leaders led to a massive alienation from government. A third came during the French war in Algeria, when angry intellectuals such as Jean-Paul Sartre effectively called for the murder of their fellow-citizens:"To shoot down a European is to kill two birds with one stone, to destroy an oppressor and the man he oppresses."

This alienation reached full florescence during the Vietnam war, when American dissidents waved Vietcong flags and chanted pro-Hanoi slogans ("Ho ho, Ho Chi Minh, NLF is gonna win").

Israel offers an extreme case of internal subversion. Arabs, one-sixth of the population, owe little allegiance to the Jewish state and sometimes openly call for violence against it or oppose its very existence. Some Jewish academics have also called for Arab violence. This climate has even led to several cases of Jews assisting Arab terrorists.

At present, loyalty to one's home society is no longer a given; it must be won. Conversely, hating one's own society and abetting the enemy is common."Traitor," like"bastard," has lost its stigma.

This new situation has profound implications. In warfare, for example, each side must compete to attract the loyalty of both its own and the enemy's population. In World War II, the Allies fought Germany and Japan; now, they focus not on whole countries but on the Taliban or Saddam Hussein, hoping to win Afghan or Iraqi allegiance.

This can lead to novel complexities: in the build-up to the Iraq war of 2003, anti-war organizations in the West effectively took Saddam Hussein's side, while the coalition in turn emphasized its Iraqi supporters. In the war on terror, the battle to win allegiances looms large and is fluid.

Treason as a concept is defunct in the West. To succeed in war, governments need take this change into account.

This article is reprinted with permission by Daniel Pipes. This article first appeared in the New York Sun.