In late 1951 Linus Pauling received an invitation to a special meeting of the Royal Society designed to address the questions British researchers had about his and Corey's protein structures. The date was set for May 1, 1952. In January, Pauling sent in a routine application to renew his passport. Instead of issuing a passport, Mrs. Ruth B. Shipley, head of the State Department's passport division, wrote Pauling that "the Department is of the opinion that your proposed travel would not be in the best interests of the United States." His request was refused.

Pauling was irritated but not surprised. Passports had become a political weapon since the passage of the Internal Security Act of 1950, which broadened the government's power to restrict the travel of political dissidents. Shipley, a fervent anti-Communist, took advantage of her position to refuse passports to anyone she and the State Department's security personnel - or the FBI, with which she kept in close contact -- suspected of being too far left and too loud about it. Pauling was a committed leftist and opponent of nuclear bombs. He had been accused of being a Communist (he was not). But the evidence was enough for Shipley.

Pauling's English hosts were incredulous when they heard that the guest of honor was denied the chance to visit. One of them later recalled "the shock that it produced, the outrage at the stupidity of the State Department at detaining the great man as if he were a dangerous character."