If you work full-time in a normal paid job, then you are pretty clearly a “worker” for the purposes of EU law.
But what if you are working part-time at McDonald’s in a host member state? Or you are a student, but you work a bit to give yourself some cash? Are you considered a “worker” for the purposes of EU free movement law?
The Danish government very generously summarizes some of the European Court of Justice (ECJ) case law on who might be considered a worker:
When is a Union citizen/an EEA national deemed to be a worker under EU law?
It depends on a concrete assessment of the specific circumstances of each case whether a Union citizen/an EEA national, including a Danish national, is deemed to be a worker under EU law. What is crucial is whether a person has had genuine and effective employment. Accordingly, employment appearing to be a mere marginal supplement is excluded from the scope of application of the concept. It is therefore normally a condition that the relevant employment was for at least 10-12 hours a week.
According to the jurisprudence of the European Court of Justice it is normally a requirement that the applicant has been employed for a minimum of 10-12 hours per week, see judgment Kempf (C-139/85) and Megner and Scheffel (C-444/93).
In the case of Kempf the employment in question was 12 hours per week, and in the case of Megner and Scheffel the European Court of Justice has ruled that paid employment where the working hours normally do not exceed 18, 12 or even 10 hours per week do not exclude that the person is regarded a worker under the EU legislation.
In the judgment of Genc (C-14/09) the European Court of Justice established criteria for the purposes of the concrete and individual assessment of whether an employment for less than 10-12 hours per week is genuine and effective. These criteria may be the entitlement to paid leave, remuneration during illness, the duration of the employment, and a collective agreement applies to the employment. The employment in the mentioned case was 5,5 hours per week.
The European Court of Justice did not consider whether a weekly employment of 5,5 hours was sufficient in order to be considered a worker under EU law, or whether the employment was of a merely marginal nature. It was left to the member state to undertake this evaluation.
It is not possible to fix a lower limit for the duration of the employment for assessment purposes.
The European Court of Justice ruled in Franca Ninni-Orasche (C-413/01) that a fixed-term contract of employment for ten weeks was sufficient for the applicant to be a worker under EU law. The case concerned educational grants and led to the issue of guidelines to the local authorities about when a person is deemed to be a worker. The guidelines concern employment relationships for which a short-term contract has been concluded in advance. The guidelines fix a minimum period of ten weeks for such situations. However, it should be emphasised that a concrete assessment must be made in each case.
Accordingly, a concrete and individual assessment must be made in each case, and the ten-week period fixed by the Court in the Ninni-Orasche judgment is thus only to be seen as an example of a situation in which ten weeks of employment were deemed to suffice.
A Union citizen/an EEA national who has permanent employment, but ceases working after less than ten weeks, may satisfy the conditions for being a worker under EU law in certain circumstances, while another person having worked for more than ten weeks may not always satisfy the conditions because it is not genuine work or for other reasons.
188.8.131.52 “Worker” is defined in the Immigration (European Economic Area) Regulations 2006 as ‘within the meaning of Article 39 of the Treaty establishing the European Community’. This suggests that a worker is a person who is employed, actually or potentially, under a contract of employment and is not a self-employed person. The European Court of Justice, in Lawrie-Blum  ECR 2121, stated that the essential point is that the person provides services during a given time for and under the direction of another in return for remuneration. The EEA national’s position within the organisation, the purpose of the work, the level of income it yields (including whether or not the person has to supplement his or her income by claiming social security benefits), and whether payment is in cash or in kind, are not relevant factors.
184.108.40.206 “Worker” includes:
- job seekers
- those between jobs (for example, women who have ceased employment on becoming pregnant but who intend to resume work at some point after the birth)
- those undergoing training in their own or another field
- sick, injured and retired workers
220.127.116.11 Reliance on public funds during periods of involuntary unemployment or training does not affect the right to remain under Community law. However, while a person who has been seeking work for more than 6 months may still be a ‘worker’ for Treaty purposes, the evidential burden shifts to that person [after 6 months] to demonstrate that genuine efforts are being made to find employment and that he or she has a realistic prospect of success (R v IAT ex p Antonissen  ECR I-745).
18.104.22.168 Under Article 39(4) of the EC Treaty, the freedom of movement provisions do not apply to certain public servants (e.g. judges). The test is whether the person is responsible for exercising powers conferred by public law or for safeguarding the general interests of the state.
When I have time, I will try to expand the case law here.