Basically, their chief was being accused of international war crimes after allegations suggested he murdered an unarmed and unconscious prisoner.
Sam and Callen were able to arrest Argento, but there was still a lot of unfinished business between them.
However, Argento believed himself to be above the law due to personal connections to a senator.
NCIS: Los Angeles’ Season11 finale, called “Code of Conduct,” saw the team go up against a new kind of antagonist following Sam and Callen’s briefing on Special Warfare Chief Petty Officer Thomas Argento.