The Light is a secret council comprised of several "enlightened" members who aim to influence the evolution of humanity.
In 150,083 CMT, Nightwing said that he wanted to keep an eye on Static because Static was new and because he had once aided Light member Lex Luthor (though unwittingly). However, Nightwing admitted that the Light had manipulated most of the Team before, meaning that his previous statement was not meant to call Static's loyalties into question.
- Background information from the Young Justice Wiki that is also assumed to be canon in BZPB
- BZPB #12498 (Apr 12, 2013)