Contradiction with Exodus 23:32
This verse commands not to make covenants with inhabitants of the land, but Joshua 9:23 involves the Gibeonites who are under a covenant.
Exodus 23:32: Thou shalt make no covenant with them, nor with their gods.
Contradiction with Deuteronomy 7:2
This verse instructs not to show mercy to inhabitants, whereas Joshua shows leniency to the Gibeonites.
Deuteronomy 7:2: And when the LORD thy God shall deliver them before thee; thou shalt smite them, [and] utterly destroy them; thou shalt make no covenant with them, nor shew mercy unto them:
Contradiction with 2 Samuel 21:1-2
This passage highlights a curse on Israel due to Saul's breach of covenant, contrasting with the accepted subjugation of the Gibeonites in Joshua 9:23.
2 Samuel 21:1-2: Then there was a famine in the days of David three years, year after year; and David enquired of the LORD. And the LORD answered, [It is] for Saul, and for [his] bloody house, because he slew the Gibeonites. [enquired...: Heb. sought the face, etc]