There are different levels of "norms" in society - law being only one of them; although it is the ultimate one (even within law criminal law being the "most ultimate" if you can say something like that).
Ethics ("morals" - after the Latin "mos" which had serious impact on their lives) or even courtesy are also relevant norms in our societies and they can differ even more than law systems can (what's more, often they are even more powerful!)
Not everthing should be governed by law (and especially by criminal law) hence there are "Ethic Codes" for a lot of professions for instance and yes, these ethic codes should also have impacts before the "outsiders" (lawyers) interfere.
It is very hard to (literally; "legally") judge two people's emotional relationship. If a professor (doctor, boss, Ross etc.) is abusing his (her!) authority then yes, indeed, there should be legal consequences but if the relationship is true (like Alan said things like that somewhere above), other means should prevail.
Indeed, it is a very slippery field... 😲
(Sorry for the bad pun, Ross - I could't resist 😄 )
