It's a clichee, but the law doesn't have anything to do with justice… and that's not a shortcoming of any actual law, it's systematically so. Understanding that, one might even make peace with lawyers!
DAJBFirst of all, not everything is either just or unjust. Most domains which are regulated by laws are not domains of justice, because most areas of human conduct aren't. As we go about our daily business we'll rarely be prompted to think about anything in terms of justice. The fact that I'm writing this now is, I hope, neither just nor unjust. Still, while doing so, I'm in accord with most local laws and even, hopefully, good taste ;-). So, a lot of actions are neither just nor unjust, and thus, only a fraction of all laws are entering domains of justice and can thus potentially interfere with anyone's sense of justice.
Oh, no - I could never let lawyers off the hook that easily! It's true that the law often has nothing to do with justice but I would argue that, if operated correctly, then it should. If it doesn't then, by definition, it's representing injustice and, if that's the case, we'd be better with no laws at all. Even a toss of a coin would ensure a just outcome 50% of the time!
Thus, most laws shouldn't even “have something to do with justice” (to defy your loosest claim :P).
But what about the ones that do? Should they at least strive to be just?
Well, what does it mean, that “a law should strive to be just”? Does it mean that:
(1) It should accord with intuitions of justice?
(2) It should accord with some sort of objective justice?
(3) It should accord with its own measure of justice?
Obviously, I'd argue against each of the three options. The first one is ruled out pretty easily - intuitions about what is just conflict in every case. There may be a common sense about what is just in a given social context, but it would have to be justified by invoking “objective justice”. So we are left with (2) and (3). And I'd argue against both by pointing out what laws are for.
The classic positions here would be contractual theories, most notably Hobbes' Leviathan. It supposes that states are created in order to establish social conduct. Without states human beings would end up in a natural order, an idealized state in which life would be “solitary, poor, nasty, brutish, and short”. Laws, in turn, are rules of conduct specifying the state's form. According to Hobbes, any state is better than none. And let's suppose that the worst state would be one made up entirely of unjust laws. It would still be a justified state.
Q.E.D.: Laws and justice are logically independent :D
You see, I haven't even been talking about the actual practice of the law today. I'm sure that - having a background in law - alejkhan would have a thing or two to say about that :D (I remember some discussions about the depravity of actual legal systems with her :P)
Also, a quick remark on why it is so tempting to think that laws “should have something to do with justice”:
I think that is because “just” is a normative term, just like “good” and “beautiful”. These terms work like: "If A can be (insert normative term), A should be (insert same normative term)." Anything that can taste good, should taste good! I think the fallacy lies in supposing that laws are in some way more deeply intertwined with justice than, say, your neighbor's treating his wife. Somehow, we expect lawyers to exemplify justice, more often than we expect our next man to do so.