> Then do a perpetual lease, or 999 year lease, or pay every year, or [...]

A perpetual or 99 year or 999 year lease is constructively a sale. Anything which is constructively a sale is banned.

Anything which is not constructively a sale will be rejected by the buyer, because they actually want to own the domain and not pay the danegeld to the squatter in perpetuity or be subject to extortionate price increases after they've committed to using the domain by publishing it in their advertising etc.

> How would you enforce a prohibition of leases?

If you offer to provide someone with use of a domain name in exchange for more money than you pay to the registrar to register it, you lose the domain name.

> Plus, the tricky bit here is there are lots of reasons for a domain owned by entity A to be used by entity B (companies might be related, might just be allowing a friend to use a domain, etc.)

You can use it all you want as long as you never pay them for it.

It doesn't matter if you can get around this with complicated corporate shenanigans because you can't sell that to arbitrary strangers who don't actually want to pay a premium for an unused domain.

If you advertise it in such a way that strangers understand you to be constructively selling the domain then they report you to the registry and you lose the domain, which then becomes unregistered and they can go register it for the ordinary nominal fee. If you don't advertise it in such a way that strangers understand you to be constructively selling the domain then you will have a much harder time finding anyone to pay you for it, as intended.

This isn't like drugs where both the buyer and seller want the transaction to happen. The seller wants the transaction to happen and the buyer wants the seller to go out of business and DIAF so the domain will be unregistered and they don't have to pay a shakedown tax for it. It's optimized for putting the sellers out of business because that's what the buyers want -- because the sellers provide no value to anybody and nobody but themselves wants them to exist.

> I don't think it's defeatism at all, by my estimation it will do very little or nothing at all, while creating a hassle for everyone. I guess I could be wrong about that, but that's what I'd expect.

We have a longstanding counterexample: Trademarks. You can't register a trademark without using it and you can't sell it.

And the latter is practically in name only -- you can sell the "goodwill" associated with the trademark and transfer the trademark with it.

Yet with as little as that, we don't have companies squatting on millions of trademarks or shaking down small businesses who just want to use a name nobody is already using.