One is  the justice of God and  ours through Jesus Christ, by which we are justified: 'of God' [(or 'God's')] because from God; 'ours,' because in us; 'of Christ' [(or 'Christ's')] because through Christ.
Last chapter of the fourth draft of the Tridentine decree on justification dated 11 December 1546 (CT V, -700-), as reproduced in P. Pas, "La doctrine de la double justice au Concile de Trent," Ephemerides theologicae Lovanienses, 30 no 2/3 (April/September 1954): 48 (5-53). "This will become in the definitive text [of 13 January 1547]: 'iustitia nostra . . . a Deo nobis infunditur per Christi meritum'" ("what is called our justice, because we are justified by its abiding in us, is that same justice of God, in that it is imparted to us by God through the merit of Christ" (Tanner, vol. 2, p. 678)). Fill this out with the analysis on pp. 37 ff.