Apologies for the U.S.-centric reference. Part 52 of
the FCC's regulations establish the basis for exclusive
authority, administrative mechanisms, and substantive
requirements for the use of E.164 numbers in the U.S.
http://www.access.gpo.gov/nara/cfr/waisidx_05/47cfr52_05.html
The remark was intended to raise the challenge of devising
any "Infrastructure ENUM Requirements" in an IETF document,
including definitions, when the actual authority to articulate
just about everything in the document resides with national
regulatory authorities. Typically, to produce what is contained
in the document, must be undertaken through a public rule
making or consultative process. Few, if any, have done so.