I'm not really an expert in the area; have just run across some sessions on it at the general yearly AI conferences I attend (AAAI, ECAI, and/or IJCAI). The keywords "legal reasoning" and "legal argumentation system" will get you quite a lot of stuff though. The latter bleeds into general "argumentation systems", since one way of modeling legal reasoning (though not the only one) is that it's a specific sub-species of debate or argumentation, rather than a specific sub-species of logical inference. (Of course, you might ask: isn't debate ideally logical as well? Empirically, it seems, the answer is: not entirely.)