Permissive Action Link - Usage of PALs By Other States

Usage of PALs By Other States

The increase in the number of nuclear-armed states was a similar cause for concern for the United States government for reasons similar to the original impetus for PALs. Thus, since the 1960s, the US has offered its own PAL technologies to other nuclear powers. The US considered this a necessary step: if the technology were kept secret, it would only be half as effective as possible, since the other power in a conflict might not have such safety measures.

In the early 1970s, France was an early recipient of United States assistance on this critical element of nuclear security. The Nuclear Non-Proliferation Treaty (NPT) went into effect in 1970 and precluded treaty members (including the US) from directly disseminating technology related to nuclear weapons development or enhancement. In order to get around this prohibition, the US developed a legal trick: "negative guidance". French nuclear scientists would regularly brief US scientists on French developments in the field of PALs, and the US scientists would tell their French counterparts whether they were on the right track. In 1971, the US also offered its technology to the Soviet Union, which developed a similar system.

In the early 1990s the People's Republic of China requested information to develop its own PALs. The Clinton administration believed that to do so would give too much information to the Chinese about American weapon design, and therefore, refused the request.

In 2007 the UK Government revealed that its nuclear weapons were not equipped with Permissive Action Links. Instead, the UK's nuclear bombs to be dropped by aircraft were armed by just inserting a key into a simple lock similar to those used to protect bicycles from theft. The UK withdrew all air-launched bombs in 1998. The current UK Trident warheads can also be launched by a submarine commander with the support of his crew without any code being transmitted from the chain of command.

Detailed information about PAL systems design and their use is classified, although these mechanisms have been offered to Pakistan for protection of their nuclear weapons. In the end, the US decided that it could not do so for legal reasons; the Pakistanis were also concerned that such technology would be sabotaged by a "kill-switch" that the US could operate. However, many experts in the field of nuclear technology in the US government supported the publication of the PAL system because they considered Pakistan's arsenal as the world's most vulnerable to abuse by terrorist groups.

Whether it’s India or Pakistan or China or Iran, the most important thing is that you want to make sure there is no unauthorized use. You want to make sure that the guys who have their hands on the weapons can’t use them without proper authorization. —Harold M. Agnew, former director, Los Alamos National Laboratory

In November 2007, the New York Times revealed that the US has invested 100 million USD since 2001 in a secret program to protect Pakistan's nuclear arsenal. Instead of transferring PAL technology, the US provided helicopters, night vision and nuclear detection devices, as well as training to Pakistani personnel in order to prevent the theft or misuse of Pakistan's nuclear material, warheads, and laboratories.