Since the UK’s vote in favour of Brexit, the free movement of workers has emerged as the key battleground of Britain’s future negotiations on a new relationship with the European Union. German chancellor Angela Merkel and other EU leaders made clear that free movement is fundamental to the EU, and that if Britain wants to retain access to the single market it is non-negotiable.

Although the public debate frequently refers to free movement of people, it is really the free movement rights of workers that are given most protection in the EU. And it is this free movement of workers, and their rights, which will be most contested in Brexit negotiations.

Free movement of workers is the third of four freedoms established in the European Economic Community’s founding Treaty of Rome – the others are free movement of capital, goods and services.

The 1992 Treaty of Maastricht created the legal status of “EU citizen”, and later secondary legislation accorded certain rights to such EU citizens. In practice, these “rights” are limited further by the ways they are interpreted and applied in member states, including in the UK.

Free to roam

An EU national who moves to another EU country to live is exercising their rights to move to, and reside in, that second country as an EU citizen.

EU citizens who have been living in another member state for less than five years must be “self-sufficient”. For the first five years, they may not be “an unreasonable burden” on the welfare system of their country of residence. What counts as an unreasonable burden is defined by each individual country, but usually limits the extent to which EU citizens have “recourse to public funds”.

In the UK, this means that incoming EU citizens do not have a right to receive social support on the grounds of financial need. As a result, income support, housing benefit and a range of other means-tested benefits are not generally accessible to all EU citizens until they have been in the country for five years.

In practice, though, the entitlements for EU citizens hinges on their employment status and under certain conditions.

Moving for a new job

A migrant who moves to another EU country and takes up “genuine and effective” employment is considered to be a worker. Workers, who can either be employed or self-employed, are entitled to move and live in another EU member state without restriction. They are also entitled to equal treatment with nationals in employment and access to social benefits after the first three months.

The UK, along with a number of other member states, has tightened its criteria for what counts as genuine and effective work.

Jonathan Brady/PA Wire

Losing a job

If a migrant who moves to the UK is employed for a while and then becomes unemployed, they are either classified as a “jobseeker” or what’s called a “retained worker”. A retained worker must have been employed for at least six months in genuine and effective work. They keep the legal status of worker and are entitled to the same social security and residence rights as nationals. In the UK, a person can keep this intermediary status for up to six months.

Changes to key criteria introduced in 2014-15 restricted EU nationals’ access to social benefits in the UK. If someone’s previous employment does not meet the threshold for genuine and effective work, then they may lose entitlement to unemployment benefit. This may affect their right to reside in a country after six months. In the UK, employment on less than £150 per week is subject to tests for the migrant to prove it is genuine and effective. Employment in a number of short-term jobs, and zero-hours contracts could also jeopardise a migrant’s status as a retained worker.

After six months, a retained worker must also have a “genuine prospect of work” to keep that status. This term is very tightly defined – such as having a job offer letter from an employer. In the context of the UK’s precarious labour market, increasingly strict interpretations of these conditions by Job Centre staff may be excluding significant numbers of EU nationals from accessing their formal social rights.

Looking for work

There are effectively two kinds of “jobseeker”. First, someone who has been employed, but for less than six months, or in work which is not considered “genuine and effective”. And second, a migrant who moves to another EU country to look for a job: they have a right to stay and look for work for six months.

Due to equal treatment legislation, after the first three months of living in a country, jobseekers have some entitlement to benefits that are designed to support the search for employment (usually unemployment benefit). They can only access these benefits for three months, and to access them, they must also show a close link with the domestic labour market. In the UK, all EU migrant jobseekers are excluded from accessing universal credit as it is classed as a general social assistance benefit rather than an unemployment-related benefit.

Route to permanent residency

An EU citizen who lives in a second member state for five years or more, with no absences for longer than three months, is a permanent resident. This status applies automatically and there is no requirement to apply to be a permanent resident. It confers special protections against deportation and generates rights to have “recourse to public funds”, irrespective of employment status.

If an EU citizen is self-sufficient and meets national residency requirements, there are no formal limits on how long they can live in another member state. But it is possible to lose this right to reside, notably, if the migrant is “an unreasonable burden” on the host state. If an EU citizen loses this right to reside, they can be deported; although the criteria for deportation are high – such as very high threats to public health or the public good – and difficult to enforce.

What’s clear is that the law in this area is complicated. In 2014 and 2015, several national courts asked for rulings from the EU’s Court of Justice to clarify the rights of EU citizens in practice. In light of this complexity, we should treat the public discussion so far about how to treat free movement in Brexit negotiations as oversimplified and premature. In the meantime, whether “citizens”, “workers” or “jobseekers”, the future of EU nationals resident in the UK has become more uncertain and precarious.