"For years, observers have warned of the looming threat of unfunded pension liabilities. Some dubbed the danger the “pension tsunami,” and it has hit an increasing number of U.S. cities, including Vallejo, Stockton and San Bernardino in California and the city of Detroit, which have sought chapter 9 relief in bankruptcy court.1 Despite the attention given to these cases, chapter 9 filings are relatively scarce, and many significant issues remain to be resolved by the courts. One unanswered question is whether a municipal debtor in bankruptcy can propose to pay its pension debt2 less than in full, even when applicable state constitutional provisions provide that such obligations must not be impaired." [excerpt]