Clive asks: "Given that continental shelf rights are inherent, what are
the legal implications for coastal States that miss the deadline?"

I don't have before me now either the rule setting the May 12 deadline,
or the authority of the Commission to rule upon the submissions made to
it in timely fashion.  But speaking from general legal principles, I
think the origin of the rights in question, whether inherent or
otherwise, would not make much difference.  IF a party to a multi-party
compact agrees to have its rights recognized by the other parties
according to the decision of a commission upon submissions to be made by
a deadline, and then it neither meets the deadline nor secures an
extension, it has WAIVED its right to have the untimely submission
considered by the commission.  It does not matter for purposes of the
WAIVER what source of the original right was, and the waiver is not of
the underlying right (which might still be recognized), but only of the
right to have its submission CONSIDERED IN DECIDING the underlying
right.  

There are some circumstances in which a waiver is ineffective -- for
example a waiver by a consumer of consumer protection legislation is
ordinarily not effective -- but those exceptions would not seem to apply
in this situation.  I repeat that this is only the general (American)
legal principle, and those more familiar with how these procedures
actually work may know better than I whether this principle applies.
But that's a horseback opinion from an American lawyer who is only an
amateur on boundary and maritime issues.

David Phillips
San Francisco