ID laws are on a state-by-state basis, since liquor sales are regulated by the individual states. Under California law (CA Bus & Prof Code 256660), it is unlikely to be acceptable. The law provides the following as allowed forms of identification:
(a) Bona fide evidence of majority and identity of the person is any
of the following:
(1) A document issued by a federal, state, county, or municipal
government, or subdivision or agency thereof, including, but not
limited to, a valid motor vehicle operator’s license, that contains
the name, date of birth, description, and picture of the person.
(2) A valid passport issued by the United States or by a foreign
government.
(3) A valid identification card issued to a member of the Armed Forces
that includes a date of birth and a picture of the person.
The law does not actually require you to check IDs, rather the law says that if you do, you have a defense against prosecution or loss of license:
(b) Proof that the defendant-licensee, or his or her employee or
agent, demanded, was shown, and acted in reliance upon bona fide
evidence in any transaction, employment, use, or permission forbidden
by Section 25658, 25663, or 25665 shall be a defense to any criminal
prosecution therefor or to any proceedings for the suspension or
revocation of any license based thereon.
A wristband is not bona fide evidence, and it doesn't matter if one gets one only after presentation of acceptable ID.
The law does not define "federal, state, county, or municipal government" and does not say "of the United States". It is well known that Queensland is a state, in Australia, and the Australian government says it has a federal government. It is reputed that (except for passports), businesses have a practice of not accepting non-US government IDs, out of an abundance of caution. Such caution would be unnecessary if there had been a court case ruling that Australian government IDs are bona fide IDs under the ID law, but that has not happened. Nor has the legislature reworded the law.
For comparison, here is what is accepted in Washington state (WAC 314-11-025):
(a) Driver's license, instruction permit, or identification card of
any state, or province of Canada, from a U.S. territory or the
District of Columbia, or "identicard" issued by the Washington state
department of licensing per RCW 46.20.117;
(b) United States armed forces identification card issued to active
duty, reserve, and retired personnel and the personnel's dependents,
which may include an embedded, digital signature in lieu of a visible
signature;
(c) Passport;
(d) Merchant Marine identification card issued by the United States
Coast Guard; and
(e) Enrollment card issued by the governing authority of a federally
recognized Indian tribe located in Washington, if the enrollment card
incorporates security features comparable to those implemented by the
department of licensing for Washington driver's licenses.
As far as I know, no state accepts proxies such as "wristband given by a party who checks IDs", or "photocopy of government ID".
