A federal judge presiding over litigation spawned by the massive Gulf of Mexico oil spill has dismissed all claims against the manufacturer of a chemical dispersant that was used to break up crude gushing from BP's blown-out well.

U.S. District Judge Carl Barbier ruled last week that federal laws shield Illinois-based Nalco Co. from liability over the government's use of Corexit after the 2010 spill.

Lawyers for cleanup workers and coastal residents exposed to the dispersant had argued Nalco isn't immune from claims it supplied a defective product that wasn't safe for use in the Gulf.

But the judge said the claims would create an "obstacle to federal law" if he allowed them to proceed.

More than 1.8 million gallons of dispersant were used in responding to the spill.