In mid-1986 Barlow became the CIA's delegate to the Nuclear Export Violations Working Group (N.E.V.W.G.), a newly formed top-secret panel that brought together the policy, law-enforcement, and intelligence communities in an effort to stop illegal American exports to non-nuclear nations. After a few failed sting operations, Barlow became convinced that the officials in the State Department were warning targets of sealed arrest warrants in FBI operations and illegally approving export licenses for restricted goods. Barlow and others in the working group stopped sharing their plans with the State Department. In July 1987, the FBI arrested Arshad Z. Pervez, a Pakistani-born Canadian, as he attempted to buy twenty-five tons of a specially strengthened steel, for which the primary use would be a uranium enrichment program, according to Barlow. This arrest was highly publicized and attracted the attention of the Asian and Pacific Affairs Subcommittee, chaired by Representative Solarz. Retired Army Major General David W. Einsel, then working for the CIA, and Barlow were asked to testify before that committee in a classified briefing. Einsel gave evasive answers when asked if Pakistan had attempted to purchase anything that would have been a violation of the Solarz amendment, either directly or via a third party in a different country. Solarz then asked essentially the same question of Barlow, who replied that the CIA knew of “scores” of Pakistani attempts to violate American export law. Barlow said that after that testimony, he was so harassed by Einsel and other senior CIA personnel that he resigned in 1988, though not before receiving the CIA's Exceptional Accomplishment Award. In 1989 he was hired as a proliferation analyst for the Department of Defense. He was in a chain of command below Stephen J. Hadley, then Assistant Secretary of Defense for Global Strategic Affairs, who reported to the Under-Secretary of Defense for Policy when Dick Cheney was the Secretary of Defense. During the debate over the sale of F-16s to Pakistan in 1989, the U.S. administration was constrained by the 1985 Pressler amendment of the Foreign Assistance Act which prohibited the sale of any matériel or armaments which might assist in the development or delivery of nuclear weapons. Barlow's analysis of Pakistan's nuclear program indicated that Pakistan possessed the capability to use the fighters to drop nuclear bombs, and the report which he submitted to Dick Cheney concluded that the F-16 sale indisputably violated the NPT and the Solarz and Pressler Amendments.