Regulation (EU) 2016/399 of the European Parliament and of the Council of 9 March 2016 on a Union Code on the rules governing the movement of persons across borders (Schengen Borders Code)

Preamble:
‘(6) Border control is in the interest not only of the Member State at whose external borders it is carried out but of all Member States which have abolished internal border control. Border control should help to combat illegal immigration and trafficking in human beings and to prevent any threat to the Member States’ internal security, public policy, public health and international relations.‘

...

Handvest van de grondrechten van de Europese Unie