Is it Iran's right to develop it, or the USA's right to block it? And if you can, base your answer according to International Law.
It is their right to develop a peaceful nuclear program.
Is their program a cover for a weapons program?
Should they be allowed to develop a weapons program?
If you lived in Israel would you allow it?
Does the idea of the Iranians with a nuclear deterrent bother you at all given their history of extremism, terrorism, local hegemic ambitions, and their close proximity to critical oil fields and shipping lanes?
Right, wrong, international law? Sounds good and all, but everyone will be sorry if those nuts get nukes.