Burma, Cambodia, Canada, the People's Republic of China, the Democratic Republic of Vietnam, France, India, Poland, the Republic of Vietnam, Thailand, the Soviet Union, the United Kingdom, and the United States signed a Declaration which together with the statement of neutrality by the Royal Government of Laos of July 9, 1962, entered into force as an international agreement on the date of signature July 23, 1962.
The 14 signatories pledged to respect Laotian neutrality, to refrain from interference — direct or indirect — in the internal affairs of Laos, and to refrain from drawing Laos into military alliance or to establish military bases in Laotian territory. The Laotian government pledged to promulgate constitutionally its commitments which would have the force of law.
However, the agreement was violated in when the Democratic Republic of Vietnam established a supply line through "neutral" Laotian territory for supplying the Viet Cong insurgency against the government of South Vietnam.
More specifically, during the Second Indochina War the North Vietnamese obtained the cooperation of the Lao People's Revolutionary Party (Pathet Lao) in constructing and maintaining the Ho Chi Minh Trail which passed through the length of Laos. Thousands of Vietnamese troops were stationed in Laos to maintain the road network and provide for its security. Vietnamese military personnel also fought beside the Pathet Lao in its struggle to overthrow Laos' neutralist government. Cooperation persisted after the war and the Lao communist victory.