10 Important Star Trek Details That Are Almost Never Mentioned
4. Starfleet's Death Penalty
Starfleet and the Federation have reputations for being very humane with prisoners. They do not practice torture, and usually prefer to rehabilitate violent people through therapy, rather than locking them up. Despite this, they're remains one crime we know of that was once punishable by death in the Federation.
After Captain Pike's visit to Talos IV in the Original Series pilot episode The Cage, Starfleet deemed the powers of the Talosians too powerful to be public knowledge, and classified them under General Order 7, which simply stated, "No vessel under any condition, emergency or otherwise, is to visit Talos IV." The punishment was death.
Starfleet feared what people would do to the Talosians to harness their ability to make dreams reality, and also what the Talosians would do to them in return. Because of this, they thought a highly severe penalty of death would be a good deterrent, however, the only time Starfleet found someone to be in violation of General Order 7 (Spock in the episode The Menagerie), they decided to let them off.
Presumably this law was done away with after The Menagerie, as Picard stated in the Next Generation episode Justice that Starfleet has no death penalty.