The Lateran Council 649 AD(cf Denzinger 263 & 264)
D 263
Canon 10. If anyone does not properly and truly confess according to the holy Fathers two wills of one and the same Christ our God, united uninterruptedly, divine and human, and on this account that throught each of** His
natures the same one of His own free will is the operator of our salvation, let him be condemned.
(note the singular of “His” - there is only one Person, and that Person is God the Son.
God cannot sin.)
D 264
Canon 11. If anyone does not properly and truly confess according to the holy Fathers two operations of one and the same Christ our God uninterruptedly united, divine and human, from this that through each of His natures He **naturally is the same operator of our salvation, let him be condemned.
(Again, it is the Person of God who operates both wills - the human will and the divine will. There is only one Person in Jesus, and that Person is the Second Person of the Trinity.)
The Council of Constantinople, 680 AD
Denzinger 291
And so we proclaim two natural wills in Him, and two natural operations indivisibly, inconvertibly, inseparably, unfusedly according to the doctrine of the holy Father, and two natural wills not contrary, God forbid, accordinbg as impious heretics have asserted, but the human will following and not resisting or hesitating, but rather even submitting to His divine and omnipotent will. For,** it is necessary **that the will of the flesh act, but
that it be subject to the divine will according to the most wise Athanasius. For, as His flesh is called and is the flesh of the Word of God, so also the natural will of His flesh is called and is the proper will of the Word of God as He Himself says: “Because I came down from heaven, not to do my own will but the will of my Father who sent me”(cf John 6:38), calling the will of the flesh His own. …
SO, THE CHURCH TEACHES:
“1. CHRIST COULD NOT HAVE SINNED”
(I know you didn’t want personal reasoning, but I couldn’t resist on D263 & 264. But I did put it in really tiny print so it would be easy to ignore!

)