Who exactly rules the United States? According to the nation's founding documents, the sovereign power over the republic is its people. They elect legislators to represent them in making the nation's laws. Through an indirect process, they choose an executive to administer the national government, who enforces those laws and also conducts day-to-day foreign policy in both wartime and peacetime.

But whenever the president of the United States wants to make lasting or especially significant changes, the Constitution demands Congress's involvement. That applies specifically to foreign policy in three ways: First, only Congress can declare or create a state of war. Second, the U.S. Senate must ratify all treaties with foreign powers. Third, Congress can cut off authority and funding for policies it opposes.

President Obama's nuclear deal with Iran's theocratic regime has critics of many different ideological stripes, and their criticisms at least deserve to be heard as part of the process of a major policy change. The deal is very heavy on immediate sanctions relief for Iran and very light on verification of its compliance. The lifting of the arms embargo seems to serve no legitimate purpose and is likely to facilitate Iran's continued support of international terrorism. What's more, Obama's negotiators inexplicably failed to include several no-brainer demands, such as the release of Americans being held in Iran.

But the deal has been struck. Under the framework established by the U.S. Constitution, Congress should now have its say. It is, after all, a co-equal branch of government, and the Constitution insists on its involvement in creating foreign policy.

Unfortunately, though, this is not what Obama plans to do. Instead of bringing the Iran deal home to Washington for approval by Americans' elected representatives — even under a process that is heavily skewed in his favor — Obama has instead committed to take it to the United Nations Security Council first, where its approval is assured, thus making it international law. Thus, instead of presenting the United Nations with an agreement that American elected officials have united behind, Obama will instead present a fait accompli to a Congress that had no say before the United Nations made it binding.

Obama's presidency has ushered in a grotesque expansion of executive power — not only in this but in many other matters as well. In some areas, the Supreme Court has stood up to him, at times unanimously. In others, it has not.

In expanding his power, Obama merely stands on the shoulders of his predecessors, but this still makes him history's tallest president so far. He has claimed the unilateral power to make war (in Libya), and to amend laws that Congress has already passed (especially Obamacare). He began his presidency by carrying through to completion the Bush administration's economic bailouts, which he completed in part by making a lawless mockery out of the nation's bankruptcy code.

Obama's unilateralism on Iran is even more dangerous. The founders' wisdom in requiring congressional involvement in major foreign policy questions has been vindicated by time. Presidents who ignored it have either made bad solo decisions (such as military involvement in Vietnam) or later faced public humiliation, as when Woodrow Wilson helped create the League of Nations without first gaining support for it in Congress.

Before committing the U.S. to Iran sanctions relief, Obama must go first to Congress, as Republicans are currently demanding, lest he face the same fate. The deal he has struck is both substantive and controversial, and therefore merits full deliberation by the people's elected representatives.

If Obama follows through on his plan to go it alone, he will not only be rejecting the founders' wisdom and the sovereignty of the electorate, but he will also be isolating himself. He will have staked his entire presidency on something he knows that Americans' elected representatives will not support, and history will deal with him all the more harshly should his deal fail.