Although the Schengen Borders Code only permits the reintroduction of controls at internal borders for a maximum duration of six months, several EU member states, including Austria, Germany, France and Sweden among others, quasi-automatically extended controls every six months since 2015. This resulted in a state of quasi-permanent controls at internal borders. The reasons invoked by these member states were essentially identical: threat of illegal migration and terrorism.

The bigger question in the case before the CJEU was the tension between the future of an EU without border controls and the free movement rights of EU citizens on the one hand and the security interests of member states on the other.

In its judgment on Tuesday, the CJEU held that a member state may temporarily reintroduce internal border controls in the event of a serious threat to public policy and internal security. However, these controls may not exceed the total duration of six months laid down in the Schengen Borders Code. Only if there is a new serious threat to public policy and internal security Member States may reintroduce internal border controls for another maximum period of six months. The CJEU thereby emphasized that the area without internal borders constitutes “one of the EU's greatest achievements”.