In international law, odious debt, also known as illegitimate debt, is a legal theory that says that the national debt incurred by a despotic regime should not be enforceable. Such debts are, thus, considered by this doctrine to be personal debts of the government that incurred them and not debts of the state. In some respects, the concept is analogous to the invalidity of contracts signed under coercion. Whether or not it is possible to discharge debts in this manner is a matter of dispute.
The concept has antecedents dating back to the 1800s and support from diverse fields such as economics, philosophy, political science, history, and law.
The concept of odious debt was formalized in a 1927 treatise by Alexander Nahum Sack, a Russian émigré legal theorist. It was based on two 19th-century precedents—Mexico's repudiation of debts incurred by Emperor Maximilian, and the denial by the United States of Cuban liability for debts incurred by the Spanish colonial regime.
Sack wrote:
When a despotic regime contracts a debt, not for the needs or in the state's interests, but rather to strengthen itself, to suppress a popular insurrection, etc, this debt is odious for the people of the entire state. This debt does not bind the nation; it is a debt of the regime, a personal debt contracted by the ruler, and consequently, it falls with the regime's demise. The reason why these odious debts cannot attach to the territory of the state is that they do not fulfill one of the conditions determining the lawfulness of State debts, namely that State debts must be incurred, and the proceeds used, for the needs and in the interests of the State. Odious debts, contracted and utilized for purposes which, to the lenders' knowledge, are contrary to the needs and the interests of the nation, are not binding on the nation – when it succeeds in overthrowing the government that contracted them – unless the debt is within the limits of real advantages that these debts might have afforded.