Get Congress or the Cabinet to invoke the 25th amendment. Pass the pass the Restricting First Use of Nuclear Weapons Act of 2017. Impeach him. Pass a law that requires the approval of the Secy of Defense or the Secy of State for a nuclear first strike. https://www.commondreams.org/views/2017/10/16/5-myths-about-war-north-korea-make-americans-think-they-are-safe
Over 135 countries agreed at the UN to sign the Treaty on the Prohibition of Nuclear Weapons. Two nuns, Carol Gilbert and Ardeth Platte, spoke here in Colorado recently about how young people worked very hard this year at the UN to form a coalition to produce a treaty to ban nuclear weapons. Once 50 countries have ratified the treaty, it will become law. Desmond Tutu, the Dalai Lama, Jody Williams, Ai Weiwei, Herbie Hancock, and Martin Sheen all support the treaty. Countries that have nuclear weapons refused to participate in drafting the language of the treaty. The nuns had earlier served sentences for pouring their blood on top of the cover of a nuclear armed missile silo in Colorado. http://www.icanw.org You can ask banks to divest from nuclear weapons companies. LIST of companies involved in nuclear weapons
http://www.postandcourier.com/news/south-carolina-attorney-general-sues-federal-government-over-plutonium-at/article_6c748d84-7c48-11e7-a766-c794f1f45b13.html The US and Russia both committed to each clean up 34 tons of weapons grade plutonium. This need to be safeguarded and prevented from getting into circulation, both because it only takes a few pounds to make a bomb and also because it is deadly, and so needs to be safely stored and secured.
Jim Green of Friends of the Earth writes in Counterpunch on the 6 year anniversary of Fukashima that the nuke business is sick and dying. http://www.counterpunch.org/2017/03/14/terminal-decline-fukushima-and-the-deepening-crisis-of-nuclear-energy (photo from the environmental justice atlas)
California's only nuclear power plant will be shut down and replaced with renewable energy, energy storage, and increases in energy efficiency. This is a great victory as it will make California safer by removing the risk of a nuclear accident from rising seas, an earthquake, or terrorism. Also, it was made by organizing cooperation between environmental groups, unions, and workers. Link.