Which of the following is not included under key aspects of neutrality in International Law ?

The law of neutrality rests on the neutral State's duties of abstention (giving no help to either side), prevention (stopping belligerents from using its territory) and impartiality (treating the belligerents equally), and on the belligerents' duty to respect the inviolability of neutral territory.

Interference in the conflict is the opposite of neutrality; a neutral State that interferes loses its neutral status.