Solidarity under duress: Defending state vigilantism

May European Union (EU) member states, in the pursuit of enforcing the norms of ‘EU justice’, unilaterally adopt harmful policies that are ordinarily impermissible in the course of voluntary cooperation amongst democratic states? Though conditions of permissible vigilantism are strict and only rarely met, there are some basic EU duties the compliance with which each individual member state is permitted to enforce unilaterally. Such measures are sometimes permissible even if European community law says otherwise: to the extent that European law prevents states from enforcing these duties, it lacks authority.