Refuse to pay government debt incurred for unlawful and oppressive purposes...it is the personal debt of those who ordered it to be incurredThere is an established legal principle that people should not have to repay their government's debt to the extent that it is incurred to launch aggressive wars or to oppress the people.
These "odious debts" are considered to be the personal debts of the tyrants who incurred them, rather than the country's debt.
Wikipedia gives a good overview of the principle:
In international law, odious debt is a legal theory which holds that the national debt incurred by a regime for purposes that do not serve the best interests of the nation, such as wars of aggression, should not be enforceable. Such debts are thus considered by this doctrine to be personal debts of the regime that incurred them and not debts of the state. In some respects, the concept is analogous to the invalidity of contracts signed under coercion.
The doctrine was formalized in a 1927 treatise by Alexander Nahum Sack, a Russian émigré legal theorist, based upon 19th Century precedents including Mexico's repudiation of debts incurred by Emperor Maximilian's regime, and the denial by the United States of Cuban liability for debts incurred by the Spanish colonial regime.
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http://www.washingtonsblog.com/2010/02/refuse-to-pay-government-debt-incurred.html