A Starfleet regulation requiring a commanding officer who is emotionally compromised by the mission to give up command, used by James Kirk to take the Enterprise from Spock.
Regulation 619 states that a command officer who is emotionally compromised by the mission at hand must resign his command. It appears in the 2009 film Star Trek.
After Nero destroys Vulcan and kills Spock's mother, the acting captain Spock maroons the insubordinate Kirk on Delta Vega. There Kirk meets the elderly Spock from another timeline, who tells him of the regulation and urges him to show that his younger self is unfit, since only Kirk in command can stop Nero.
Back aboard the Enterprise, Kirk goads Spock about his mother until the Vulcan loses control and nearly strangles him on the bridge. Spock then acknowledges that he is compromised and steps down, and Kirk, whom Pike had named first officer, takes the captain's chair.