Mr. Manchin, a Democrat facing re-election in a red state that's reeling from prescription painkiller and heroin abuse, said the Justice Department requested his proposed changes to the law, which had breezed through Congress without much scrutiny.
"We're talking about fair trade," Mr. Manchin said. "Free trade hasn't worked well for West Virginia. It really hasn't. We have lost thousands of jobs. And we're [talking] about a fairness to the system."