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What is irregular migration?

As much as migration is on the news and an axis of so many political divides, it may come as a surprise that there is no international legal definition for migrant. Instead, it is an umbrella term that includes several subgroups—one of which in policy conversations is referred to as ‘irregular migrants.’ Sentiments toward irregular migration are especially strong with often individuals on the right calling for stricter border controls and individuals on the left calling for greater protection of human rights. But who are irregular migrants? And why is that the term used?


Who is an irregular migrant?

In the simplest of terms, irregular migrants are individuals who either

  1. Enter without the necessary legal permission (referred to as irregular entrants)

  2. Stay in a country without the necessary legal permissions (referred to as irregular residents)

  3. Are in some way in violation of the country's immigration laws such that if it were discovered they could be forced to leave

Patterns and policies related to irregular entrants and residents are often referred to as flows and stocks. As with many things, there is debate about the definition and the correct terminology.


Why are they referred to as irregular migrants?

The labels unauthorised, undocumented, and illegal aliens are also at times used to refer to irregular migrants, but there are critiques for each of these as being unhelpful or inaccurate. The terminology irregular evolved in contrast to regular or legal migration; a binary that is argued does not represent the complexity of migration statuses or experiences. Instead, it is proposed that irregularity should be thought of as degrees.

For example, there are different types of irregularity for irregular residents that relate to their right to residence and work:

  1. Some migrants reside irregularly (i.e. without a legal residence permit)

  2. Others reside regularly (with a legal residence permit) but are working in violation of the employment restrictions attached to their immigration status, a situation coined as semi-compliance

  3. A third dimension of irregularity relates to the formality of employment, i.e. whether or not migrants and their employers pay the taxes and social insurance contributions required by the host country’s tax regulations


How are irregular migrants different from other migrants?

Most migration to Europe is known as mixed migration—where people with different immigration statuses arrive together; these categories can include migrant workers, refugees, and asylum-seekers, among others. But the distinctions between groups can be blurred as individuals’ statuses can fluctuate between regular or irregular.

Here are just a few examples:

  • A migrant worker could enter the country legally with a work visa (regular status) but then overstay their visa (irregular status)

  • An individual could enter the country without authorisation (irregular status) but later apply for and receive asylum (regular status)

  • An individual might enter and stay in the country with a student visa (regular status) but might engage in work prohibited by the visa (irregular status)


IOM’s infographic visualises some of these categories and fluctuations:

© IOM GMDAC 2017 Retrieved here


How many irregular migrants are in Europe?

The nature of irregular migration makes reliable data challenging; it’s been referred to as counting the uncountable. But here are some of the things we do know:

  • In 2017, it was estimated that there were three to four million irregular migrants in Europe; accounting for less than 1% of Europe’s total population

  • In 2022, 330K irregular border crossings were detected, the highest since 2016; nationals of Syria, Afghanistan, and Tunisia were the most frequently reported

  • In 2023, the nationalities most reported among all migrant arrivals to Europe have been Guinea, Syria, Cote d'Ivoire, and Tunisia

  • Greece, Italy, and Spain are the European countries that receive the overwhelming majority of migrant arrivals

  • It is been hypothesised that most irregular migrants in Europe are individuals who entered through a regularised pathway but then overstayed their visas


Why does this matter?

While the labels for irregular migrants might feel inadequate, the most critical aspect of irregular migrants is that they lack some type of authorisation; this can make them vulnerable to exploitation and deportation. We know little about how the conditions of irregular migrants differ across European countries. Despite this lack of knowledge and lack of understanding of terminology, sentiments on migration are likely to remain too high.


Earlier this month, the European Parliament passed a years-in-the-making and landmark bill on migration. The New Pact on Migration and Asylum involves a set of reforms addressing screening procedures, asylum processing, integration, and border management. While it was passed ahead of the election in hopes of curbing the role that migration plays in the election, with forecasting predicting strong shifts of the right, it seems likely that migration will play a critical role in the public narrative and debate leading up to the election.


Explore more statistics about irregular migration:


Stephanie Acker is a Research Associate at the Migration Policy Centre of the Robert Schuman Centre at the European University Institute. Her research focuses primarily on refugees, asylum-seekers, and unaccompanied children including: how refugees re-make home in displacement; the role of beauty and aesthetics in refugee responses; refugee shelter programmes; refugee-led organisations; refugee self-reliance; child protection; and systems change and innovation in policy and programme response.