Using your Hunter NetID, you can access the English translation via this link to the Hunter Library website. The translation of De monarchia can be found on pp. 111-73.
Cassell, A., & Vernani, G. (2014). The Monarchia Controversy : An Historical Study with Accompanying Translations of Dante Alighieri’s Monarchia, Guido Vernani’s Refutation of the Monarchia Composed by Dante and Pope John XXII’s Bull, Si Fratrum. Washington: Catholic University of America Press.