EU member states cannot imprison foreigners simply because they illegally entered the country, the bloc's top court ruled Tuesday, in a case involving a Ghanaian woman apprehended in France.
The European Union has been grappling with an influx of migrants and asylum seekers since last year. Many member states are now seeking to crack down on economic migrants, who have no right to stay, in order to better manage those deserving international protection.
The case before the European Court of Justice (ECJ) predates last year's migration surge, but could have a bearing on decisions taken in response to the high number of arrivals.
In March 2013, Selina Affum of Ghana was stopped by French police at the Channel Tunnel crossing to Britain on board a coach travelling from the Belgian city of Ghent to London.
Affum presented a passport bearing another person's name and photo. She was placed into custody for illegally entering France. But Affum challenged her treatment and a French court turned to the ECJ for advice on the legality of her imprisonment.
The Luxembourg judges ruled that taking into custody a non-EU national only for illegal entry violates the bloc's rules and undermines their effectiveness, since this delays procedures to send the person back to their country of origin or a country of transit.
The court said that EU rules only allow imprisonment if foreigners stay on despite being the subject of a return procedure; if there is a risk of the process being "compromised"; if the person breaches a ban on re-entering the member state; or if they commit other crimes.
In two other migration-related cases on Tuesday, the Luxembourg judges also ruled that asylum seekers are allowed to challenge their transfer from one EU member state to another.
Under the bloc's rules, asylum seekers are supposed to file their claim for protection in the first member state they reach.
But the ECJ found that asylum seekers can appeal their transfer to another member state if they believe EU rules were inappropriately applied, even when the other country has already agreed that it has responsibility for the asylum claim.
The cases featured an Iranian man who sought asylum in the Netherlands in 2014 despite having been granted a visa in France the year before, and a Syrian man whose asylum claim in Sweden was rejected in 2014 because he had applied for protection in Slovenia.
Both men challenged their transfers back to France and Slovenia.
The Iranian man said he had only spent one night in Paris before returning home and that the asylum claim he later filed in the Netherlands was his first. The Syrian man argued that he had left Slovenia for more than three months before seeking asylum in Sweden and claimed that the asylum system in Slovenia had deficiencies.