In Justice in Season 1 Picard prevents the aliens from executing Wesley Crusher because he considers their legal system privative and overly legalistic. And the aliens themselves tell him earlier in the episode "you could just take your boy, and we'd have no way of tracking him because of your superior technology" and Picard swears he won't do that (despite eventually doing exactly that).

You are right that there are a couple episodes (Homeward with Worf's brother, Pen Pals with Data and his friend, Suddenly Human with the human orphan raised by aliens) where the opposite happens. In Homeward and Pen Pals you have others forcing Picard's hand to act opposite; in Suddenly Human the Enterprise was matched with a technologically equal foe and therefore couldn't act unilaterally.

Picard was at his best when he acted the most right-wing (acted as the standard-bearer for his culture and people, looked out for his people above outsiders). That I think is one of the interesting paradoxes of the Trek shows: they are inherently left-wing in philosophy and outlook, but to make them palatable to a wide audience they have to add right-wing traits to the characters; but it is those right-wing character traits that make the characters (and therefore the shows) endearing.