Historically and traditionally, "law" was considered to be something that lawyers and judges "discovered," rather than something a group of legislators made up and voted on. The law was something that private parties used to settle disputes among themselves, not something that the state, or some groups in society, used to force their will upon others.
_Freedom and the Law_ explores this distinction, between the old idea of law and what people today call law, which is really legislation. Leoni persuasively argues for a return to the imperfect but vastly superior Roman law, or the English common law, as a means of restoring the individual liberty that the state has been destroying in modern times.
It is a challenging book, and perhaps best suited for those with a strong background in history, law, and/or economics. I first attempted to read it when I was younger, and stalled after the first chapter or two. Coming back to it with more education and understanding, I've found a lot to appreciate.
Incidentally, this volume actually contains two books: _Freedom and the Law_ and _The Law and Politics_. The latter is a relatively short collection of lectures from the 1960's, but will be of particular interest to anyone who's studied public choice economics, as Leoni examines the then-new ideas of Duncan Black, James Buchanan, and Gordon Tullock.