How are conflicts between constitutional and treaty obligations resolved?

Question

The present Constitution of Bolivia, which came into effect on the 7th of February 2009, has this to say about coca (an English translation follows the original Spanish):

Artículo 384. El Estado protege a la coca originaria y ancestral como patrimonio cultural, recurso natural renovable de la biodiversidad de Bolivia, y como factor de cohesión social; en su estado natural no es estupefaciente. La revalorización, producción, comercialización e industrialización se regirá mediante la ley.¹

Article 384. The State shall protect native and ancestral coca as a cultural patrimony, a renewable natural resource of the biodiversity of Bolivia, and a factor of social cohesion; in its natural state it is not a narcotic. Its revaluation, production, commercialization and industrialization shall be regulated by law.

Between the 23rd of September 1976 and the 1st of January 2012 (when it was officially denounced by the Bolivian government), Bolivia was a signatory to the United Nations Single Convention on Narcotic Drugs, which states:

Article 26, paragraph 2. The Parties shall so far as possible enforce the uprooting of all coca bushes which grow wild. They shall destroy the coca bushes if illegally cultivated.²

and

Article 49, paragraph 2(e). Coca leaf chewing must be abolished within twenty-five years from the coming into force of this Convention as provided in paragraph 1 of Article 41.

On their face, these constitutional and treaty obligations, which were simultaneously in force through most of 2009-2011, would appear to have been in direct conflict. This apparent conflict was eventually resolved (after repeated attempts to amend the Convention by Bolivian governments throughout the time Bolivia was a signatory) by Bolivia's denunciation of the Convention, as noted above.

I understand that some international treaties, however, are considered irrevocable - for instance, I've read that there is no legal mechanism by which a member state can leave the European Union - and conversely, constitutional amendments often require ratification by referendum, which obviously is not guaranteed to succeed.

In such a case, how is the conflict resolved? I'm interested here in both the theoretical (which obligation is considered to have precedence) and the practical (what is likely to actually happen).

On a side note, I'd also be interested to hear about other states which confer (or have conferred) protected or otherwise special status on particular substances, plants or animals.

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UPDATE: Bolivia has now reacceded to the Convention, with the reservation that it "reserves the right to allow in its territory: traditional coca leaf chewing; the consumption and use of the coca leaf in its natural state for cultural and medicinal purposes; its use in infusions; and also the cultivation, trade and possession of the coca leaf to the extent necessary for these licit purposes."³

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References:

1. Constitutión Política del Estado Plurinacional de Bolivia (PDF)

2. Single Convention on Narcotic Drugs, 1961 (PDF)

3. Associated Press, 11 January 2013

Note: the linked PDF for reference #2 is a very poor scan of a paper document. If anyone can find a better link, feel free to edit; the referenced text is on pages 246 and 272 of the currently linked PDF.

Answer 1

Typically a sovereign nations constitution represents the highest law of the land, as it defines the framework for all other laws that that come after it. Using the United States as an example then it becomes clear what would occur in this situation for the United States as it clearly declares that a Treaty is to be a "Law of the Land"

This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding.

For the United States however the Constitution is the supreme law of the land and supersedes everything else, meaning that if such a Treaty were ratified that it directly violated the Constitution then it would be invalid and could be challenged in the Supreme Court.

International Law however disagrees. A Treaty is the highest form of law between two countries and is binding between two states as a contract (barring the treaty doesn't violate any other International Laws and that the Treaty was passed valid per the states rules on ratification of Treaties).

This applies to all 112 countries that have ratified the Vienna Convention on the Law of Treaties.

http://untreaty.un.org/ilc/summaries/1_1.htm

Again however, this International Law on treaties is meaningless to the United States as it had only signed the Law of Treaties but did not in fact ratify it per our Constitution. This essentially means that the United States deems itself perfectly legal to enter into, leave or break treaties of its own will regardless of International Law.

This also happens to be the case for Bolivia (Dark green are countries that Ratified the Treaty of Laws, Light Green are Signatories)!

Interestingly enough I think the case can be made that the Treaty is completely invalid for Bolivia.

1. Bolivia did not ratify the Vienna Convention on Law of Treaties so they are not legally bound to it by International Law.

2. Even if it had been a ratifying state, it is still invalid because the Bolivian government was wrong to ratify it according to Article 27, Vienna Convention on the Law of treaties. A party's consent to a treaty is invalid if it had been given by an agent or body without power to do so under that state's domestic law.

IANAL, but I think a strong case can be made that in this specific case that the Bolivian Treaty is invalid.

How this can be resolved is dependent on how the Constitution of that country specifies potentially invalid laws are to be challenged. Typically this would be through a Higher Court of some kind.

Answer 2

In Russia and in other countries with the same legal tradition, the Constitution has the supreme legal power. International treaties come second, and other (non-constitutional) federal laws come third.

Any international treaty that violates the Constitution is invalid in the part that violates, while may remain in force in other respects.