Mosse's importance lies in his work on Japan's Meiji Constitution and his continuation of Litthauer's Comments on the German Commercial Code.

Mosse was born into a prominent Jewish family in Grätz, in Prussia's Grand Duchy of Posen.

He then studied law at Berlin University in 1865 thanks to the financial support of his older brothers, and passed his first state examination in 1868, and the second one in 1873.

Eventually, he was appointed judge of the state court in Berlin, which was the highest position a Jew was allowed to achieve in Germany at the time.

Mosse is credited with having convinced Ito Hirobumi that the Prussian-style monarchical constitution was the best suited for Japan.