<s>There's a proposal for one: http://area51.stackexchange.com/proposals/67858/law.

If it attracts enough people, we'll set up a site on the topic. </s> 

There is a [Law Stack Exchange](http://law.stackexchange.com/) site now.
See also: https://meta.stackexchange.com/questions/76974/how-can-i-propose-a-new-site