John Gill Commentary Judges 11:23

"So now Jehovah, the God of Israel, hath dispossessed the Amorites from before his people Israel, and shouldest thou possess them?" — Judges 11:23 (ASV)

So now the Lord God of Israel has dispossessed the Amorites
from before his people Israel
It is his doing, and not the work of the Israelites; it is he that dispossessed the Amorites, and put the Israelites into the possession of their land, and therefore they enjoy it by a good tenure:

and should you possess it ?
what through the blessing of God on their arms they have obtained by conquest, and he has settled them in; did they conquer, that you should possess what they conquered? did their God put it into their hands to deliver it into yours? did they fight to recover for you what you had lost, and to put you into the possession of it?

did not they fight in their own defence, and their enemies and their land fell into their hands, and by the laws and right of nations became theirs? and can you expect to possess it? what reason is there for it?