Nor should we confuse open borders with a lack of national sovereignty. Consider the case of Spain and the EU. Until 1991, Spain had an open border with North Africa. Migrant workers would come to Spain for seasonal work and then return home. In 1986, the newly democratic Spain joined the EU. As part of its obligations as a EU member, it had to close its North African borders. The closing of the borders did not stop migrant workers trying to enter Spain. Instead, they took to small boats to cross the Mediterranean and smuggle themselves in. This was the start of the ‘migration crisis’.
Spain had exercised national sovereignty by keeping its borders open.
Closed borders were imposed by Brussels.