An attorney representing an objector to a $3 billion securities settlement involving Brazil’s state-run oil company Petrobras must pay class counsel $10,000 for attempting to derail the deal in exchange for a payoff, a federal court ruled Sept. 21.

Attorney Joshua R. Furman filed “a kitchen-sink brief that purports to identify inequities relating to at least a dozen aspects of the proposed settlement, none of which had the slightest merit,” Judge Jed S. Rakoff wrote for the U.S. District Court...