I certainly don't think 'legal' necessarily implies 'moral'. Sometimes they're the exact opposite. There are also things that aren't legislated that should still guide us.

For example, it's not illegal to be an asshole to someone. But that doesn't make it okay either. It's not something that's ever going to be legislated, and I don't think it should be. Tax rules, on the other hand, should be legislated, because the same people will always take advantage of them if they can. I don't see purely voluntary tax as working (though a certain type of libertarian loves to suggest exactly that).