it was always significant to me that sam wanted to become a lawyer. because the most compelling reason for why the winchesters hunt the way they do–ruthless, uncompromising, at the first mistake you make we will be there–is because in the face of real monsters, the justice system can do absolutely nothing. no shifter can ever be convicted by a jury of his peers. no insanity defense can protect those who have been possessed, who were not just out of control but were not even present for the crime. dean and sam are judge, jury, and executioner because the alternative is no semblance of justice at all. hunters are what happens where the rule of law flounders in the face of what it cannot comprehend.
so think of sam’s interest in law (in criminal law, from the very specific shot we see of his law textbook in “what is and should never be”) as not a rejection of the judge-jury-and-executioner moral attitude as a hunter but as an extension of it, as a way to bring the strong moral compass that has to animate and carry you onwards when you’re a hunter into the apple-pie lifestyle, which is so relativist in its ethics. what do polite people not talk about? politics or religion. anything where you might accidentally step on your neighbor’s sensibilities, might accidentally accuse them of being immoral. even when sam wants that, he wants to puncture it, rupture it.
(this is a post about justice in supernatural but it could just as easily be about sam winchester and the impossibility of a normal life; i mean, look at his hobbies: serial killer trivia; his thirteen-year-old magic phase, these are interests existing on the border between the normal and the abnormal, bringing death and magic into a place where it normally doesn’t belong. just like sam.)