The Treaty on the Prohibition of Nuclear Weapons is clear-  any assistance with prohibited acts including producing, developing, manufacturing, deploying and stationing nuclear weapons- is also prohibited.

The specific language of the treaty that relates to questions of assistance is contained within Article 1, which reads:

1. Each State Party undertakes never under any circumstances to:
   
   (a) Develop, test, produce, manufacture, otherwise acquire, possess or stockpile nuclear weapons or other nuclear explosive devices;
   
   (e) Assist, encourage or induce, in any way, anyone to engage in any activity prohibited to a State Party under this Treaty;
   
   (f) Seek or receive any assistance, in any way, from anyone to engage in any activity prohibited to a State Party under this Treaty;

Financing, including private sector financing, is a recognized form of assistance, as understood in the Chemical Weapons Convention, the International Convention for the Suppression of the Financing of Terrorism. Also, Security Council Resolution 1540 has long been interpreted to cover companies and individuals engaging in prohibited WMD proliferation actions.

While the word financing doesn’t specifically appear in the list of prohibitions in the nuclear ban treaty, it’s become regular practice for countries to recognise financing as a specific subset of assistance (which is explicitly prohibited). During treaty negotiations, many countries made it clear that assistance would include all forms of financing, just as it does for chemical weapons. During negotiations South Africa made the point that “financing is implicitly covered in the sub articles and any state that knowingly engages in such activities would be in contravention of its obligations under this treaty.”

To compete for nuclear weapons related contracts, companies involved must secure capital for research, development and cash flow. To do so, they borrow funds, or seek underwriting for bond or share issuances. The provision of these financial services enable the private sector to maintain its role in the perpetuation of nuclear arsenals. When seeking financial assistance, the companies involved in the nuclear weapon industry do not look to fund new projects, rather, they raise capital for general corporate purposes. Providing this type of financing is assisting with the production of nuclear weapons, and outlawed by the TPNW.

The Treaty thus provides a legal footing to strengthen responsible investment practices and avoid profiteering from preparations for mass murder.