33 Thus already in the preamble of the decree of 7th July 1624, by which the adoption of the Latin rite was forbidden only to the clergy, it was laid down that priests of the Latin rite were to be warned not, when hearing confessions, to encourage the lay faithful to adopt it. Warnings to the same effect were repeated again and again, and the Apostolic Nuncios in Poland by order of the supreme pontiffs made every effort that they should have the desired result. That the mind and judgment of the Apostolic See on this subject did not change even in later times is shown by the letter of our predecessor Benedict XIV to the bishops of Lvov and Przemysl in 1751 in which inter alia this is found: "Your letter written on 17th July has reached us; in it you justly complain of Ruthenians going over from the Greek to the Latin rite, whereas you are well aware, venerable brethren, that our predecessors have detested and we detest these changes of rite, since we very much desire that preservation and not the destruction of the Greek rite." The same pontiff therefore promised that he would remove all hindrances in the matter and would finally prohibit such going over to the Latin rite in a solemn decree. However, the adverse circumstances and conditions of the times did not permit that his wishes and promises should have their desired outcome.
Source: Orientales Omnes Ecclesias (Vatican.va)