Ghetto is the least defined term in the English language.
Most folks think that the term 'ghetto' started up in Italy in the 1500s. It was supposed to have started up in Venice, Italy, and had some connection the Jews who lived in a particular 'quarter' of the city. In some ways, it was supposed to mean a highly populated or dense area of some town, with particular groups of low-income residents, and that 'quarter' or district was seen as run-down by the local population of the city.
You can go to several dozen westernized states or countries, and find ghetto-like conditions in effect. Some morphed into this over decades....some took just one single decade.
Europe as a whole....through the words of politicians....will say that no ghettos exist. Then you get into a car....drive through various urbanized areas of France, Germany, Sweden, Italy, etc....and quietly look at a neighborhood that fits the general description of a plain old-fashioned ghetto.
In most cases, what you will find through historical situations, is that a economic growth occurred, demanding more labor. This labor is not necessarily high-tech or craftsman-like skills....but the type that a journeyman or ranked-amateur might possess. So they move into this city or town, and take up jobs. Their pay-scale is not at the high end. They look for affordable housing. And they take residence.
At some point, that neighborhood which has the new labor residents, will come to grasp that large numbers of these workers are not natives of the country, and are more of a migrant-worker than anything else.
These neighborhoods go through a stage of older residents moving out, and newer (migrant-type) families moving in. There's nothing to prevent this, nor would you go and create some stupid rule to say only 10-percent of a neighborhood can be migrants.
After a while, you start to notice in these ghettos....there's a couple of different categories of migrants. There's the group which really wants to integrate, be part of society in this new nation, and enjoy the fruits (economic success, safety, stability, limited corruption, etc).
Then you have the group which just kinda arrived....mostly in a shock stage even at the one-year point....and grumbles daily because it's outrageous on the cost-of-living/taxes and just too many stupid rules.
Then you have the group which realize their craftsmanship abilities are non-existent and other than stocking shelves in some grocery or washing dishes at a restaurant.....they will never make enough money to enjoy life....so they discover that selling drugs is profitable and engage in this new trade to succeed in life. This is also the group that bands together other loser individuals, forms up gangs, and establishes their 'territory' within their new land.
The ghetto goes through growing pains as the residents now come to realize that there just aren't any residents from this society around them....it's just other immigrants. Then they come to realize that various youth-gangs have formed up and tend to be up things that bother or irritate the residents. And finally, when the crap has really hit the fan and they need cops to re-establish order....the cops really aren't capable of handling this type of environment....so when you call for the cops, it's not a normal crew of two guys, but a squad group of ten, with four cops out front and guarding the vehicles that they arrived in (only in force will they come).
The country itself now? Well....they have a birth-rate and reproduction problem, and the wise-guys felt that any immigration was a good idea, but then come to realize that you needed to funnel these people through, determine integration potential, and limit entry to a degree. But now? It's a bit too late. And the cops just grin when you chat about this in public and try to soften the crime aspects of this new society.
You could talk about getting strict and enforcing the law, but that means arresting a large number of the new migrants/immigrants, and that gets negative press coverage by your elitist journalists. So you just let the issue lay there and hope that something comes along to fix it. Gang-wars would be a plus because they'd attack each other and eventually take down their own numbers. If you look at Sweden over the past six months....there are minor examples of gang-wars going on. You see the same episode in Duisburg, Germany....where several gangs are now hyped up against each other and street episodes occur every couple of weeks.
It is.....what it is. You can't undo this or go through some revision. You will simply have to learn how to deal with this and eventually enlarge your police force. Life in Europe has permanently changed.