Japan
Japan rejects the Treaty on the Prohibition of Nuclear Weapons after all nuclear powers boycott the treaty. This rejection happened days after the United Nations said there was enough signatories for it to go into effect and following pressure from atomic bomb survivors to adopt it. Japan states it is unrealistic to pursue the treaty with both nuclear and non-nuclear states being sharply divided over it, and instead the country will serve as a bridge to narrow the gap between the two sides.
Sources: ABC News