In normal times, it would not be controversial for the Israeli prime minister to address a joint session of Congress. These are not, alas, normal times.

The Obama administration is reportedly considering a U.S.-Iran nuclear deal that would, as Benjamin Netanyahu said last week, “allow Iran to become a nuclear threshold state.” In other words, we are reportedly on the verge of accepting the eventual nuclearization of Iran at a time of the mullahs’ choosing. While the administration is defending its strategy as an example of sophisticated and pragmatic realpolitik, there is good reason to believe that President Obama is poised to commit a blunder of historic proportions. It certainly does not inspire confidence when the president threatens to veto Senate legislation designed to ensure Iranian accountability.

Which brings us to today’s speech by Prime Minister Netanyahu. Did House Speaker John Boehner’s invitation to the Israeli leader violate diplomatic protocol? Did Netanyahu have domestic politics in mind when he accepted it? These questions are not unimportant, but they are much less important than the potential consequences of Obama’s Iran deal.

Writing last week in the Wall Street Journal, Harvard law professor Alan Dershowitz put the significance of Netanyahu’s speech in proper perspective:

Not only should all members of Congress attend Mr. Netanyahu’s speech, but President Obama — as a constitutional scholar — should urge members of Congress to do their constitutional duty of listening to opposing views in order to check and balance the policies of the administration.

Whether one agrees or disagrees with Speaker John Boehner’s decision to invite Mr. Netanyahu or Mr. Netanyahu’s decision to accept, no legal scholar can dispute that Congress has the power to act independently of the president in matters of foreign policy. Whether any deal with Iran would technically constitute a treaty requiring Senate confirmation, it is certainly treaty-like in its impact. Moreover, the president can’t implement the deal without some action or inaction by Congress.

Congress also has a role in implementing the president’s promise — made on behalf of our nation as a whole — that Iran will never be allowed to develop nuclear weapons. That promise seems to be in the process of being broken, as reports in the media and Congress circulate that the deal on the table contains a sunset provision that would allow Iran to develop nuclear weapons after a certain number of years.

Once it became clear that Iran will eventually be permitted to become a nuclear-weapon power, it has already become such a power for practical purposes. The Saudis and the Arab emirates will not wait until Iran turns the last screw on its nuclear bomb. As soon as this deal is struck, with its sunset provision, these countries would begin to develop their own nuclear-weapon programs, as would other countries in the region. If Congress thinks this is a bad deal, it has the responsibility to act.