He was an influential representative of the pre-Humanist scholastic ius commune tradition, and one of the leading jurists of his time together with Felino Sandeo, Antonio Cocchi Donati and Bartolomeo Socini.

[1] Born into a Milanese noble family, Decio studied the humaniora and then law in Pavia under his brother Lancelotto and Jason de Mayno.

[2] Following departure of the French from Milan in April 1512 and the destruction of his home, his library and his manuscripts by the Swiss army, he followed Louis XII's call to Valence and became a member of the Grenoble parlement.

Celebrated in his time as a teacher and jurist, Decio was the most prominent and among the most prolific of the last generation of commentators following in the tradition of Cinus, Bartolus and Baldus.

His commentary of 1521 on the De regulis iuris of the Digests, begun at Valence and completed at Pisa, sets out the methodological principles and criteria for a systematic approach to the study of law.