The children of Israel didn't strike them, because the princes of the congregation had sworn to them by Yahweh, the God of Israel. All the congregation murmured against the princes.
and all the congregation murmured against the princes; not only for taking such an oath, but chiefly because they restrained them from smiting the Gibeonites, and taking their substance for a prey; their eager desire of revenge, and of seizing their goods, and inhabiting their cities, raised a murmur in them against the princes. This is to be understood not of the whole body of the people at Gilgal, but of all that party that was sent to Gibeon, and of the princes that went with them.