What is the Napoleonic code? Why is Stanley so interested in it?

Napoleonic code is the French civil code established under Napoléon I in 1804. The code forbade privileges based on birth, allowed freedom of religion, and specified that government jobs should go to the most qualified. Stanley says he uses it so he can follow what his wife does. 

You see, under the Napoleonic code – a man has to take an interest in his wife’s affairs