Is murder illegal because its wrong? Or is murder wrong because its illegal?

a great question -- a deep one, and an old one -- basically grounded in the classic theistic question addressed by Plato (in Euthyphro) and many others since -- does God command us not to do things (such as murder) because they're wrong, or are they wrong (simply) because God commands us not to do them ... Stephen's response is excellent, but I'll offer another angle. Re the first half -- is murder illegal b/c it's wrong -- no doubt those legislators who have illegalized murder are at least partly (maybe primarily/exclusively) motivated by its wrongness (that's the sociological/empirical question) -- but presumably your question is meant to be more general, i.e. not merely restricted to murder, whose 'wrongness' most everyone can agree to (though not everyone). If you were to ask 'of all those things that are illegal, are they illegal b/c they are wrong?' surely for many/most of them the answer would be 'no.' It's illegal to go through a red light, not b/c going thru red lights is morally wrong but b/c...
Law

Is there a philosophical point of view to the use of of marijuana? How would a philosopher think about smoking marijuana?

interesting question -- but why would a philosopher think any differently on this subject than anyone else? are you asking whether pot smoking should be legal? then it's a public health issue, a privacy issue, etc., and then lots of experts can weigh in from all sorts of perspectives (with partly philosophical positions, but not necessarily 'professional philosophers'' philosophical positions ...) are you asking whether it's good to smoke pot? does a good life include it? then we do get to standard philosophical questions, but then there wouldn't be "a" philosopher's way of thinking about it, there would be the usual debates about different conceptions of ethics. of course, no doubt, some people become philosophers partly as a result of their pot-smoking experiences, which no doubt would subsequently inform their philosophial opinions -- about many things, including about pot smoking. anyway, this may not have been particularly useful, but perhaps it's a start! ... best, ap