The temporal displacement policy was a series of guidelines instituted by Starfleet which obligated its officers to take no action which could alter the course of history if they were to travel through time. After having accidentally traveled back in time from 2371 to 2024, Julian Bashir expressed his dissatisfaction with the temporal displacement policy when informed by Commander Sisko that they could do nothing to help the hundreds of people who would be killed in the Bell Riots, which would occur in only three days time. (DS9: "Past Tense, Part I")