The American Society for Legal History awards scholars each year in a number of categories ranging from dissertation to books to articles and digital projects. Each prize is detailed on the page linked above.
The John Phillip Reid Book Award is awarded annually for the best monograph by a mid-career or senior scholar, published in English in any of the fields defined broadly as Anglo-American legal history.
The Peter Gonville Stein Book Award is awarded annually for the best book in non-US legal history written in English. This award is designed to recognize and encourage the further growth of fine work in legal history that focuses on all regions outside the United States, as well as global and international history.