Iran signed the Nuclear Non-Proliferation Treaty (NPT) back in 1970. Israel still refuses, to this day, to sign the NPT. Israel won't submit to nuclear inspections. Iran allowed IAEA inspections until last year in June, when US and Israel bombed the Iranian nuclear sites.

Then in September last year the IAEA and Iran reached an agreement on inspections, but that's in trouble with the current US & Israel combined attacks on Iran.