[address-policy-wg] Multi-regional allocation question - transversing RIRs

I have a large multi-regional client, who's main base is in the USA.
They are about to get a /19 from ARIN since they are multi-homed and have
about 32 sites, but they also have about 5 sites in APNIC and the another
5 in the RIPE region.  Do they have to become members in each RIR to get
multi-homed allocations, or should one RIR handle it all?

Would the answer to that above question change if the IP blocks used in
APNIC and RIPE wouldn't be announced locally in those regions but would
rather be MPLSed back to the USA and from there all Internet access would
be allowed (thereby making the IP blocks pseudo-USA blocks)?

References:
http://www.ripe.net/info/resource-admin/rir-comp-matrix-rev.html
This doc seems to imply with the 1.2 section statement of "Membership is
globally open without condition" that ARIN can allocate IPs anywhere, as
can RIPE, which sort of contradicts the section "Emergence of the RIRs"
located at:
http://www.ripe.net/info/resource-admin/rir-system.html

So any official guidance is appreciated.

Thanks,
Hank