It's a lease—with conditions

The most important parallel to the Hittite document, however, is what happens to the city as a result of the harem. Mursili gives the site of the city to his god Tešub to be used as a pasture for his bulls. Joshua likewise gives the cities to Yahweh for Yahweh to use, but Yahweh has a different use in mind. Mursili destroyed his city, but Joshua leaves most of them intact, because Yahweh’s intended use of them requires them intact: Yahweh is going to lease the land back to Israel. Because the land is ḥerem, Israel cannot make use of it for itself, but it belongs to Yahweh, and so Yahweh can do whatever he wants with it. What Yahweh chooses do with his land is to allow Israel to use it, provisionally on Israel’s fidelity to the covenant.— The Lost World of the Israelite Conquest, 177

<idle musing>
I really like this idea—that YHWH is leasing the land back. It's like a return to Eden in a way. God is starting again (and again, and again, and…)
</idle musing>