“Therefore do not defile the land which you inhabit, in the midst of which I dwell; for I the Lord dwell among the children of Israel” (Numbers 35:34 NKJV).

What would “defile the land?”
The blood of unatoned murder is a defilement of any land. Not just the murder itself, but the murder that isn’t justly punished. As the Lord told Cain after he murdered his brother, “Your brother’s blood cries out to Me from the ground” (Gen. 4:10).
The Lord gave authority to human government to both limit and punish sin. As the apostle Paul wrote to the Romans, The ruler “does not bear the sword in vain; for he is God’s minister, an avenger to execute wrath on him who practices evil.” The Lord will not long dwell with a nation that does not execute justice.