The establishment of a Schengen-area of “freedom of movement” without border control is deemed a major achievement of European integration. Developments since 2015 have shown a renewed salience of internal borders: several countries have introduced temporary (maintained) border control, but also adjacent border-regions are increasingly invested with strategic importance. Intensified (national) border-area police-checks (art. 23 Schengen Borders Code) and enhanced bilateral police cooperation were also recommended by the European Commission as possible “alternatives” to border control, inter alia to counter so-called “secondary movements”. Both the Treaty on the Functioning of the European Union (TFEU) and explicitly the Convention Implement...