It took Sigismunt II's unilateral declaration of the incorporation into the Polish Crown of substantial disputed border regions, including most of Lithuanian Ukraine, to make the Lithuanian magnates rejoin the process, and participate in the swearing of the act of the Union of Lublin on July 1, 1569.
Zygmunt II tegi ühepoolse deklaratsiooni oluliste vaidlusaluste piirialade, sealhulgas enamuse Leedu Ukrainast, Poola krooniga liidendamisest, et Leedu magnaadid ühineks protsessiga ja osaleks vande andmisel Lublini uniooni aktile 1. juulil 1569.