Extradition Cases Reflect Strains Within the EU

Divisions in the bloc over the rule of law in several countries are threatening cross-border cooperation

BRUSSELS—Europe’s internal divisions over the rule of law in several countries are threatening cross-border cooperation among prosecutors, imperiling an initiative intended to boost public security.

The split has emerged over arrest warrants, a fast-track extradition procedure introduced in the European Union after the 2001 terrorist attacks on the U.S. to fight terrorism and other serious crimes.

The...