Prime Directive
In Star Trek it is the General Order 1 of the Starfleet and an oath every Starfleet Personnel has to take and uphold, even if it means death to them or their crew.As the right of each sentient species to live in accordance with its normal cultural evolution is considered sacred, no Starfleet personnel, Federation citizen and/or representative may interfere with the normal and healthy development of alien life and culture.
This is what often made the Prime Directive ineffective, since broad interpretive powers by Kirk would deem many cultures to be neither normal nor healthy.