Generally it's done by the company running the TLD (called the registry). Registrars like Namecheap generally can't pull these shenanigans and have to keep the

Generally it's done by the company running the TLD (called the registry). Registrars like Namecheap generally can't pull these shenanigans and have to keep their markup reasonable because otherwise people will just transfer the domain to a different registrar which doesn't pull the shenanigans.