Many who loudly insist Europe is being overrun by Islam eagerly repeat claims that France has Muslim-only "No Go" Zones.
In his now infamous Fox News appearance, "terrorism expert" Steve Emerson said these "sort of safe havens" for extremists have also sprung up in other countries.
"You basically have zones where Sharia courts were set up, where Muslim density is very intense, where the police don't go in, and where it's basically a separate country almost, a country within a country," he said.
It's a claim that has been made before and often since the attack on Charlie Hebdo last week, where the terrorists' victims included a Muslim police officer.
An online Fox News report about these supposed places in France says "neither tourists nor cops dare enter" and "poor and alienated Muslims have intimidated the government into largely ceding authority over them, prompting fears that the kind of jihad that gave rise to last week's attack in Paris is festering unchecked."
In Britain, the English Defence League (EDL) has written: "Even in our modern society it seems that so-called no-go areas are on the increase throughout the UK and Europe".
Last week, The Washington Times ran an article saying Islamists were taking over French cities "block by block". It quotes the Gatestone Institute, a conservative think-tank previously accused of Islamophobia, which said in 2011 that the "no go zones" were proliferating across Europe.
In reality, the 751 'Sensitive Urban Zones' (known by the French acronym ZUS) are more mundane, complicated and similar to impoverished areas common in cities across the world.
The French Government created the ZUS designation in a 1996 law that aimed to boost investment in neighbourhoods where people were disproportionately poor, lacking in formal education, reliant on social housing and unemployed. Each has an average of around 6,000 residents.
The law specifies the ZUSs are made up of "major high-rise estates or areas of poor housing and a sharp imbalance between housing and employment". They are in urban areas all over the country and its overseas territories, but the best known are in the Parisian suburbs.
Different ZUSs have different levels of government intervention - from tax breaks for businesses there to rebuilding social housing and providing vocational training.
The ZUS designation has nothing to do with religion or ethnicity - but they are disproportionately not white.
A 2010 study found 21% of the population of Parisian ZUSs were African immigrants, who make up 7% of urban France as a whole. In the 1990s, a quarter of all such immigrants arriving in France lived in a ZUS. A total of 30% of those of North African descent live in a ZUS.
No one denies the ZUSs are troubled. The percentage of those unemployed can comfortably run into double figures. The mayor of the Paris suburb Sevran, home to three ZUSs, told The Economist: "Here, drug trafficking has always helped circulate money. It’s how people scrape by."
The ZUSs in Paris were the epicentre for three weeks of nationwide rioting in 2005 that was so bad it led to a national state of emergency.
A car burns amid the 2005 rioting in the northern Parisian suburb of Pierrefitte, home to a ZUS
But experts told The Huffington Post UK that it was "stupid" to say that French authorities were giving up on them. Two said that the police were actually prone to invest more, not less, resource in the ZUSs - the opposite of what those, who suggest they are "abandoned" to Sharia law, claim.
Prof Paul Silverstein, an American anthropologist who has studied Algerian immigration to France, said the ZUSs were "first and foremost French areas - culturally, socially, linguistically - and no one who has spent time in a Muslim-majority country would think that they are in one".
Working out how "Muslim" the ZUSs are is difficult, he told HuffPost UK, saying that including everyone descended from immigrants from Muslim-majority countries would inevitably include those who are not religious.
He added practicing Muslims will vary in how observant they are, with some limiting the public expression of faith to "symbolic" measures such as avoiding pork or fasting during Ramadan.
He said: "Moreover, the claim that these are Muslim areas is over-stated. Areas can indeed vary dramatically in terms of their ethnic make-up, but rarely have I heard of any given building, much less a full housing project, much less a municipality being even majority Muslim."
He added: "The reality is that these are over-policed areas, that the people who live there have far too frequent interactions with the police, including frequent stop-and-frisk harassment.
"The French government has not abandoned these zones; if anything they have over-invested in them discursively and materially, and that investment has been disproportionately in terms of security and policing."
Christian Mouhanna, director of France's Centre for Sociological Research on Law and Penal Institutions, agreed, saying it was "nonsense to say that the French government has abandoned any area".
"Of course, I would not say that there is no tension with some Muslims, but to say that we have no go zones is unrealistic and stupid. There is no place where Islamic laws are enforced," he said.
"There is no place in the whole of France where the police forces don't enter a zone."
Mayor of Lille, Martine Aubry (second right) visits a ZUS in the city in 2011
He said the police often had a "very bad relationship" with locals in ZUSs that led them to typically attend an incident in larger numbers, with "two cars, four to five officers".
He added: "I personally don't know any places where I cannot enter and I'm not a Muslim. I am not sure that I would enter in some areas in the middle of the night, but it is not (a question of being) non Muslim."
Daniel Pipes, an American author and president of conservative think tank Middle East Forum, talked up the spectre of "no go" zones in a 2006 article, but came to regret it after after visiting Sarcelles, Val d'Oise, and Seine Saint Denis in the Paris suburbs, which he described as "very mild, even dull".
"The immigrant areas are hardly beautiful, but buildings are intact, greenery abounds, and order prevails," he wrote after the visit.
Pipes told HuffPost UK these areas lacked the "menacing" atmosphere in some places in the US.
The ZUS American author Daniel Pipes visited
He said: "I expected these areas to be similar to the worst areas of the United States, such as the Bronx or Detroit, where buildings are decrepit, streets menacing, and outsiders feel distinctly unwelcome.
"My experiences belied this expectation. All the immigrant areas turned out to be well maintained, with safe streets, and no sense of intimidation.
"I walked around, usually with camera in hand, and felt at ease. I encountered no difficulties at all."
While he noted their problems left them "prone to outbreaks of violence", he added: "From an American point of view, these areas are a bit confusing: potentially dangerous, yes, but in normal times very ordinary looking and with no sense of foreboding. Thus, the term no-go zone does not accurately reflect the situation."
The message to Fox News circulated by Le Petit Journal on Twitter
Sociologist Hugues Lagrange used to walk around ZUSs to conduct interviews for his research into race and immigration in France.
He told HuffPost UK: "At least in the most part of the Paris region, it is absolutely false that there were areas outside police reach and monitoring and, for me, it has always been possible to enter.
He said youths would "tease" him but more direct hostility, such as having "small stones" thrown at him, was rare.
Current affairs TV show Le Petit Journal broadcast a segment on January 13 debunking Fox News' claims about "no go" zones.
The show also circulated a message to Fox News on Twitter that said: "Verify your information, you are wrong about no go zones in France!"