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 for the Southern District of New York.

The court acknowledged that objectors can help ensure settlements are fair for unnamed...