Bolivia initially proposed an amendment to article 49, deleting the therein contained obligation that “coca leaf chewing must be abolished”. The article allowed countries only a temporary exemption, but coca chewing had to be phased out in any case within 25 years which expired end 1989 (the 1961 Convention entered into force in December 1964). By the closure of the January 31, 2011, deadline to file objections to the Bolivian amendment, 18 objections were submitted (though the one from Ukraine seemingly did not arrive in time).
Even though ECOSOC has not taken a formal decision of rejection, the number of objections and the fact that those included all G8 countries, appears to be enough to block the adoption of the amendment. The Bolivian government then decided to withdraw from the Convention and re-access with a reservation. The Bolivian House of Representatives approved the law on June 22nd, and the Senate ratified the decision on June 28th.
The next day, June 29, Bolivia withdrew from the Single Convention by presenting to the UN General Secretary in New York a formal notification of denunciation (see the press conference by Bolivian Ambassador Pablo Solon). The withdrawal will enter into effect on 1 January 2012 (see Article 46 of the Single Convention). By then, Bolivia will accede to the Convention again with a reservation on the coca leaf and its traditional uses, using the procedure established in Article 50, §3.
The official Commentary on the 1961 Single Convention mentions explicitly that (p. 476): "By operation of article 50, paragraph 3, a Party may reserve the right to permit the non-medical uses as provided in article 49, paragraph 1, of the drugs mentioned therein, but also non-medical uses of other drugs, without being subject to the time limits and restrictions provided for in article 49."
After Bolivia deposits its instrument of re-accession with the reservation, the treaty comes into force for the country again 30 days later (article 41, §2). After one month Bolivia will thus be formally a State party to the Single Convention again, and the accession procedure might even be initiated before the denunciation takes effect, avoiding an interim period where Bolivia would not be a treaty member. However, other State parties will have twelve months from the date of Bolivia’s re-accession to object to the new reservation. Unless after those twelve months one third of the parties have objected, the reservation “shall be deemed to be permitted”. In the unlikely case that one third or more State parties object, out of the total of 184 parties to the 1961 Single Convention as amended by the 1972 Protocol, the reservation would be considered invalid.
What would happen in that –unlikely- scenario, is an unsettled matter in international law. Several options are mentioned by experts in the field. First, the state’s accession “may be nullified (and its treaty membership terminated) absent a clear indication of its intent to adhere to the treaty without the reservation. Second, the state may be considered a party to the treaty except for the clauses to which its invalid reservation applied. Third and most controversially, the reservation may be severed. Under this approach, the state is deemed a party to the treaty in its entirety, including the provisions covered by its now stricken reservation” (Yale Journal of International Law, Vol. 31: 367, 2006, p. 379). The final option is that it simply remains unresolved. Reservations are an important and much-used instrument in the development of international law and in practice generally appear to remain in effect, despite any objections brought against them (Yale Journal of International Law, Vol. 31: 307, 2006, p. 307-366).
The procedure is unlikely to fail also because Bolivia’s reservation will be modeled on the one they already made when they signed and ratified the 1988 UN Convention against Illicit Traffic in Narcotic Drugs and Psychotropic Substances (see the UN treaty collection register). Parties considering to object would have to argue why they could accept a similar reservation by Bolivia under the 1988 Convention and not now under the 1961 Single Convention.