Philosophy is used for several different types of degrees and studies. In philosophy we can study and observe why people may have made those actions, or will make those actions. I also believe any and all types of studies can help legal doctrine. There is no such thing as too much knowledge.
All laws as they exist today have stemmed from a philosophical idea. The judicial system of the law is based on the fundamental philosophical difference of morals and good vs. evil. What is determined as evil and unjust is determined by a philosophical outlook upon the definition of evil, and rather or not it can be universally accepted. Therefore no legal documentation can exist without the guide of philosophical thinking.
Philosophy shapes thoughts and ideas of the day. Philosophy led to the institution of our government, and caused us to adopt a civil (written) law system instead of directly copying England's common law. Philosophy is why most crimes have to be actions, and crimes of intent are rare (and require some actions that prove intent). Why would we assume that philosophy's contributions to law have been exhausted?
I do not think that the legal profession and law in general has anything to gain by using philosophy to guide itself. These two things are very different and separate and there is no reason for them to ever one day be mixed together and to blend with one another.