Douglas is an advocate of nuclear disarmament, a supporter of the Nuclear Age Peace Foundation, sits on the board of the Nuclear Threat Initiative, and is an honorary Board Member of the anti-war grant-making foundation Ploughshares Fund. In 1998, he was appointed UN Messenger of Peace by Secretary-General Kofi Annan. He is a notable Democrat and has donated money to Barack Obama, Christopher Dodd, and Al Franken. He has been a major supporter of gun control since John Lennon was murdered in 1980.
In 2006, he was a featured speaker in a public service campaign sponsored by a UN conference to focus attention on trade of illicit arms, especially of small arms and light weapons. Douglas made several appearances and offered his opinions:
The conference is an opportunity for UN member states to build on the Program of Action and to encourage countries to strengthen their laws on the illicit trade, … an issue that affects us all … [and] while owning guns is a legal right in most countries, the illegal trade in guns continues to fuel conflict, crime and violence.