IANA is the *Naming and Addressing* Authority. But to the best of my knowledge the IANA's authority is not sufficient to guarantee Internet-wide connectivity.
There is no authority any more. May have been in the ARPAnet, *may* be in the NSFNET days. The IANA/InterNIC thing is essentially a coordination function that assumes that everyone plays and in result gives a good probability of global uniqueness in varieties of assignments. If the policies are not being accepted, the non-accepters will weight global interconnectivity against needing to provide services in a perhaps isolated environment. Many will choose global connectivity, some others may not. Example. A few weeks back or so I needed an AS number, but the InterNIC came back, after I filled out their form, with what I considered unreasonable additional requests, and I thought screw it, I don't need this, I just pick a number. The setup was semi-experimenal anyway (some routing research, but connected), and if someone complains I can fix it later, or send them after the InterNIC. So, the coordination function has failed there, and there was certainly no authority involved. I liked Dennis' note about picking reasonable targets, btw, and going for those somehow, may be doing "limits by declaration," so we find out what's reasonable, rather than dwelling in doom or no-doom about address spaces and so. That something that could be done at the NANOG meeting, with some email in advance and after?