Trading with a Friend's Enemy

Economic sanctions have been the West's response of choice to Russia's full-scale aggression in Ukraine. Predictably, speculation abounds as to what these sanctions portend for future responses to acts of interstate aggression. The principles underpinning the trading with the enemy laws of a seemingly bygone era have resurfaced but applied not to the sanctioning powers' own enemies but in solidarity with another state, at least insofar as the breaches of erga omnes obligations through armed aggression are concerned. The contemporary expansion in sanctions practice may have far-reaching repercussions.