"Given Roddenberry's goal of a television series revolving around the adventures of a space-age Captain Horatio Hornblower, it is not surprising that much of the international structure would be based upon the law as it existed during the heyday of the fighting sail. In contrast to our contemporary world, in which international telephone communications are instantaneous and where travel from any one point on the globe to any other can be accomplished in under a day's time, the planets on ST:TNG sometimes go for decades without communicating with one another, and the time to travel form one planet to another (even at warp speed) is measured in days, weeks or years - not hours. In such a decentralized legal system, there would not be enough repetition of practice to develop customary law."
January 1, 1970
https://en.wikiquote.org/wiki/Star_Trek%3A_The_Next_Generation