A handful of local officials in California who say the housing bust is a public blight on their cities may invoke their eminent-domain powers to restructure mortgages as a way to help some borrowers who owe more than their homes are worth.

Investors holding the current mortgages predict the move will backfire by driving up borrowing costs and further depress property values. "I don't see how you could find it anything other than appalling," said Scott Simon, a managing director at Pacific Investment Management Co., or Pimco,...