The editorial speaks of an accused Somali, Ahmed Abdulkadir Warsame, who was seized by American forces in international waters and who was then 'secretly held in extralegal detention' on a warship. It crticises President Obama for 'drifting toward establishing his own system of extralegal detention'.
What's that? What does 'extralegal' mean?
According to my Oxford English Dictionary, it is an adjective that describes something 'beyond the province of law, not regulated by law'. Perhaps thunderstorms are extralegal. Or sunsets. But when a government 'arrests' (i.e. kidnaps) people and then holds them secretly, denying them access to courts, this isn't 'extralegal', it is 'illegal'.
Within UN law, there is a document entitled 'Principles on the Effective Prevention and Investigation of Extralegal, Arbitrary and Summary Executions', adopted by Economic Social Council resolution 1989/65 of 24 May 1989. I can't explain why they used the term, but clearly the preferred nomenclature is 'extrajudicial' rather than 'extralegal'. An extrajudicial execution would be one carried out without judicial authorisation, and there is probably some usefulness in the concept. But an extralegal execution might better be called a 'murder'.
The New York Times is supposed to be a bit of a stickler for precise language. I'm not sure if they still have the regular columns by William Safire that offered entertaining if pedantic discussions about the meaning of words. Perhaps they could explain the difference between 'extralegal' and 'illegal'.