LONDON » The letter informing Mohamed Sakr that he had been stripped of his British citizenship arrived at his family’s house in London in September 2010. Sakr, born and raised here by British-Egyptian parents, was in Somalia at the time and was suspected by Western intelligence agencies of being a senior figure in al-Shabab, a terrorist group linked to al-Qaida.

Seventeen months later, a U.S. drone streaked out of the sky in the Lower Shabelle region of Somalia and killed Sakr. An intelligence official quoted in news reports called him a "very senior Egyptian," though he never held an Egyptian passport.

A childhood friend of Sakr, Bilal al-Berjawi, a Lebanese-Briton also stripped of his citizenship by the British government, was killed in a drone strike a month earlier, after having escaped an attack in June 2011.

Senior U.S. and British officials said there was no link between the British government’s decision to strip the men of their citizenship and the subsequent drone strikes against them, though they said the same intelligence may have led to both actions.

But the sequence of events effectively allowed the British authorities to sidestep questions about due process under British law, mirroring the debate in the United States over the rights of U.S. citizens who are deemed terrorist threats. The U.S. and Britain have a long history of intelligence sharing and cooperation in fighting terrorist threats.

The cases of Sakr and al-Berjawi are among the most significant relating to the British government’s growing use of its ability to strip citizenship and its associated rights from some Britons at the stroke of a pen, without any public hearing and only after-the-fact involvement by the courts.

Now, faced with concerns that the steady stream of British Muslims traveling to fight in Syria could pose a threat on their return, Prime Minister David Cameron’s government is pushing legislation that would give it additional flexibility to use the power, which among other things keeps terrorism suspects from re-entering the country.

In many Western countries, including the U.S., citizenship is considered a right that cannot be taken away except in very limited cases, such as serving in another nation’s military or having obtained citizenship fraudulently. Others strip citizenship from people who take another passport.

Britain, along with Israel, is one of the few countries that can revoke the citizenship of dual nationals even if they are native born if they are suspected or convicted of terrorist offenses or acts of disloyalty.

Britain is seeking to expand the practice to naturalized citizens who have no other nationality and would be rendered stateless. Citizenship, in the words of Home Secretary Theresa May, is a "privilege, not a right."

The issue is beginning to stir public debate. A government-sponsored amendment expanding the practice to naturalized citizens who have no other nationality sailed through the House of Commons this year. But on Monday, in a rare act of parliamentary rebellion, the House of Lords rejected the amendment and asked instead for a joint committee of both houses to examine whether the additional powers are necessary. The draft legislation will now return to the House of Commons.

Britain typically strips people of citizenship when they are outside the country. The procedure requires only that the home secretary find that stripping someone of citizenship would be "conducive to the public good," then sign a deprivation order and send a letter to the person’s last known address.

Loss of citizenship is effective immediately. It can be challenged in court, but that is a difficult task in most cases, given the inability of a targeted person to return to Britain for any proceedings.

"Deprivation can help disrupt the terrorist threat," John Taylor, the junior minister for criminal information, said in a recent parliamentary debate. Taylor said the government refused to be "at the whim of other countries’ nationality laws" or the view of a court.

Other countries are watching closely. A Canadian bill giving the government some deprivation powers is now before Parliament. Australia and the Netherlands are both considering drafting legislation.

In Britain, there is some unease at the implications.

Sakr, who was killed in February 2012, had appealed on the grounds that the British government was rendering him stateless. He had never sought an Egyptian passport despite being eligible for one because of his parents’ heritage.

He eventually abandoned his appeal for fear that frequent communication with his lawyer on a cellphone or computer would make him vulnerable to a drone strike by giving away his location, according to his lawyer at the time, Saghir Hussain.

Al-Berjawi was killed in January 2012, hours after using a cellphone to call his wife in a London hospital on the day their son was born.

In a case involving the U.S., a Somali-born Briton, Mahdi Hashi, was stripped of his British citizenship in June 2012 and then captured and detained on a U.S. base in Djibouti two months later. He was taken to the United States, where he awaits trial on terrorism-related charges.

"The sequence of events does not look accidental," said Hussain, who is also representing Hashi in a separate appeal against his deprivation order.

Forty-two people have been stripped of their British citizenship since 2006, 20 of them last year, according to a freedom of information request filed by the Bureau of Investigative Journalism, a research organization at City University London that first drew attention to the practice in December 2012. In Israel, by comparison, the power to revoke citizenship has been used only twice since 2000, according to the Interior Ministry there.

Cameron’s government, in power since 2010, has stripped more people of their citizenship than all the other British governments since World War II combined, said Matthew J. Gibney, an expert on citizenship at the University of Oxford.

During World War I, anti-German sentiment and concern about foreign spies first made citizenship deprivation a popular tool both here and in the United States.

The practice fell into disuse after World War II, when it became associated with totalitarian regimes like Nazi Germany. A landmark ruling by the U.S. Supreme Court in 1958 struck down a law that allowed citizenship deprivation as a punishment. Proposed legislation in Congress in 2010 to reinstate the practice did not win enough support.

In Britain, the power remained on the books but was little used until after the attacks of Sept. 11, 2001. Powers have been gradually expanded since then.

The most significant expansion of the power came in 2006, after the July 7, 2005, attacks on the London transport system that killed 56 people, including four bombers. The previous standard whether someone’s conduct was "seriously prejudicial to the vital interests" of the country was replaced with more elastic wording that allows deprivation on the grounds that it is "conducive to the public good."

The 2006 legislation was shaped by the case of Abu Hamza al-Masri, a British-Egyptian cleric the government had been seeking to strip of citizenship since 2003. He was deprived of his Egyptian citizenship while his appeal against the British order was pending, forcing the British government to drop its efforts.

Al-Masri remains a British citizen, but has since been extradited to the United States to face terrorism charges.

The latest proposed amendment may also have been inspired by a specific case in which the government did not get its way.

Hilal al-Jedda, an Iraqi-born, naturalized Briton, lost his British nationality in 2007 after being detained in Iraq on suspicion of smuggling explosives.

Out of 15 appeals, his is the only one to have succeeded. Britain’s Supreme Court ruled in October that al-Jedda could not be deprived of his British nationality because it would make him stateless: Iraq bans dual citizenship and canceled al-Jedda’s passport in 2000 when he was naturalized in Britain. The British government was forced to reinstate his citizenship on Oct. 9, 2013.

But on Nov. 1, al-Jedda was stripped of his nationality a second time, and in January the Home Office rushed the amendment before Parliament allowing deprivation even if it results in statelessness, provided that a suspect’s citizenship is "seriously prejudicial to the vital interests of the United Kingdom."

© 2014 The New York Times Company