BP has escalated an extraordinary courtroom attack on the federal judge in New Orleans presiding over the multibillion-dollar litigation concerning the 2010 Gulf of Mexico oil spill. The assault on US District Judge Carl Barbier concerns one particular battle in a larger legal war, and the oil company's aggressive strategy could come back haunt it on other fronts. Last month the US Court of Appeals for the Fifth Circuit in New Orleans blocked certain spill-settlement payments for private business claims that BP had alleged were exaggerated or "fictitious." The ruling amounted to an embarrassing rebuke of Judge Barbier, who had appointed and vigorously defended the claims administrator. Now BP has returned to the Fifth Circuit, accusing Barbier in a filing yesterday of defying the appellate court by failing to stop disputed payments to businesses whose losses the oil company contends had absolutely nothing to do with the April 2010 spill.