A Starfleet regulation, quoted by Saavik in Star Trek II, stating that a flag officer may not beam into a hazardous area without an armed escort.
General Order 15 is quoted in Star Trek II: The Wrath of Khan. As Admiral Kirk prepares to beam over to the silent Regula I laboratory, Lieutenant Saavik recites it to him, saying that no flag officer shall beam into a hazardous area without armed escort.
Kirk replies that there is no such regulation, but he gives way with good humour and lets her join the landing party with McCoy. Whether she has quoted a real order or made one up to stay at his side is left for the audience to judge.
The moment fits Saavik's habit of citing rules at Kirk throughout the film, from the Kobayashi Maru debriefing to her objection when he fails to raise shields as the Reliant approaches. Kirk later teases her that she should go on quoting regulations.