ICANN decides how the internet addresses and TLDs work at a base level. As far as I understand, TLDs have always been a monopoly for their owning registry. Verisign, the various country codes by their country's governments (or whoever they delegate to), PIR, and many many others.
That's why it was such a big deal when .net and .org were looking to change hands.
That's why it was such a big deal when .net and .org were looking to change hands.