Legal moralism is when a society creates laws based on the prevailing morality of that society. Stuff like "we think green houses are immoral, so we made a law to ban green houses".
Is there a term for the opposite influence? As in "if Y is legal, I have no problems with doing Y" as an individual viewpoint for moralism?
Probably the term Legalism is the best short term, as mentioned by others, but to put it into a larger framework, it is part of the second stage of moral reasoning in Kohlberg's stages of moral development. Level 2 (conventional), Stage 4 (Authority and social-order maintaining orientation). This makes it a higher level of reasoning than avoiding punishment or pure self-interest, but lower than reasoning that evaluates the good of the laws for society as a whole and questions them: https://en.wikipedia.org/wiki/Lawrence_Kohlberg%27s_stages_of_moral_development
I think an appropriate term for what you might be asking is "virtue jurisprudence," which overlaps with philosophical questions of ethics and morals. Aristotle popularized this concept to some extent. Ancient Greeks used the word "Arete" to refer to good morals and ethics, although it more generally can be used to refer to anything that is highly superior in its existence and translates to "excellent." In legal theory, Arete can be applied to how one interacts with the law as it relates to a virtuous quality of one's actions.
