Over the weekend, a man walked around Westminster, the center of British power, with a young girl on his shoulders and an Islamic State flag draped across his back. Photographs of the man quickly spread on social media, and many found it deeply offensive that he had cloaked himself in a flag so tightly linked to terrorism just days before the 10th anniversary of the 7/7 bombings in London.

Perhaps just as offensive to some, however, was the response of London's Metropolitan Police. Rather than arrest the man, police released a statement saying that officers had spoken to him and decided that his actions were "within the law."

Judging by some of the online response to the Met's decision, there are plenty of people in Britain who feel that it should not be legal to fly the Islamic State flag. Anxiety about the militant group, which is primarily based in Iraq and Syria, is high in Britain. Thirty British citizens were killed in a recent Islamic State-linked terrorist attack in Tunisia, and Britain is the home country of a number of Islamic State militants, including the notorious "Jihadi John," whose real name is Mohammed Emwazi.

Prime Minister David Cameron has suggested that those flying the flag of the Islamic State, which is also known as ISIS and ISIL, should be arrested. "If people are walking around with Isil flags or trying to recruit people to their terrorist cause," the British leader wrote in the Daily Telegraph last year, "they will be arrested and their materials will be seized."

On Wednesday, London Mayor Boris Johnson — a man with a high national profile — stepped into the debate, telling LBC Radio that he supported the police decision not to arrest the man. When asked why Britain hasn't banned the flag, Johnson replied simply: "We live in a free country."

This image posted Aug. 27, 2014, by the pro-Islamic State Raqqa Media Center shows a fighter waving the group's flag from inside a captured government jet after the battle for the Tabqa air base in Raqqa. (Raqqa Media Center via AP)

Britain's anguish over the flag comes at a time of international debate over the implications of flying flags and wearing other symbols. In the United States, the continuing outrage over the Confederate battle flag, which many view as a symbol of slavery and racism, has been contrasted to the post-war situation in Germany, where Nazi symbols were outlawed shortly after World War II and remain prohibited to this day.

Such a blanket ban is hard to imagine in the United States, where freedom of speech is strongly enshrined in the First Amendment: The Confederate battle flag may be removed from state property, but that doesn't entail an outright ban on the flag's private use. In Britain, where freedom of speech is protected by a number of laws, including the Human Rights Act, a German-style blanket ban would be highly unusual.

However, Britain does have a number of laws that could prohibit the flying of an Islamic State flag in certain circumstances. For example, there's the Public Order of Act 1986, which prohibits "any writing, sign or other visible representation which is threatening or abusive within the hearing or sight of a person likely to be caused harassment, alarm or distress thereby."

Helen Fenwick, a professor at Durham Law School, suggests that Section 13 of Britain's Terrorism Act of 2000 would be the most applicable to the Islamic State flag. This section makes it illegal for a person to wear an item of clothing or display the article in "such a way or in such circumstances as to arouse reasonable suspicion that he is a member or supporter of a proscribed organisation." Such a law stops short of a blanket ban on a flag — it could certainly be displayed in a college seminar on terrorist groups — but does allow the police to arrest someone if an object such as a flag indicates membership in a prohibited organization. Since June 2014, membership in the Islamic State has been illegal in Britain.

Fenwick notes that this law allows both Cameron and Johnson to be in agreement: There are some circumstances in which an Islamic State flag can be flown, and there are some in which it cannot be. In the weekend case in Westminster, the police decision against arresting the man draped in the flag suggested that authorities did not have a "reasonable suspicion" after questioning him that he was a member of the Islamic State.

For many government critics, however, the exact circumstances of when the flag could be allowed might seem ill-defined. Complicating the matter further is the nature of the Islamic State flag. As WorldViews has noted, similar flags have been flown by a number of different Islamist groups over the years, and flags that resemble the Islamic State's banner have duped people in London before: A flag in an East London council estate was investigated by police and found to be slightly different, and CNN recently mistook for the Islamic State flag a banner portraying sex objects during a gay pride march.

Other critics go further, suggesting that the British government's continuing emphasis on symbols and regulations is an attempt to avoid dealing with more difficult issues.

"That image and style are prioritized over insight and substance is a sorry statement of our times," said Bill Durodie, chairman of international relations in the Department of Politics, Languages and International Studies at the University of Bath.

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