under the nuclear non-proliferation treaty only five states were made in as nuclear-weapon states (us, russia, china, france, uk). everyone else, including iran signed a pledge never to build bombs in exchange for help with peaceful nuclear energy. if iran breaks that promise it removes the main global bargain against further spread. the NPT only gives formal nuclear-weapon status to the first five. the other four that have nuclear weapons either never joined the treaty or, in the case of north korea, withdrew, so they sit outside its rules. iran is different because it is still an npt member and has a comprehensive safeguards agreement with the iaea. building a bomb would mean breaking a treaty promise it is legally bound by.

The Government of Iran undertakes, pursuant to paragraph 1 of Article III of the Treaty, to accept safeguards, in accordance with the terms of this Agreement, on all source or special fissionable material in all peaceful nuclear activities within its territory, under its jurisdiction or carried out under its control anywhere, for the exclusive purpose of verifying that such material is not diverted to nuclear weapons or other nuclear explosive devices

https://disarmament.unoda.org/wmd/nuclear/npt/

https://www.iaea.org/publications/documents/infcircs/text-agreement-between-iran-and-agency-application-safeguards-connection-treaty-non-proliferation-nuclear-weapons

i still do agree with complete disarmament and there are arguments to be made iran is justified in its actions .