The debate on Iran sanctions is rather familiar. If you go back four years, you will see that it was the Obama campaign that made claims of weakness and fecklessness on Iran. President George W. Bush had considered the building of a multinational coalition seeking to negotiate with Iran as one of his foreign-policy legacies, but Obama officials were critical, saying it offered “weak carrots and weak sticks."

Yet Ryan’s critique of the sanctions and the U.N. diplomacy during the Obama administration is missing certain nuances:

1. The U.N. Security Council resolution is only the tip of the iceberg. Obama’s initial outreach to Iran, which was largely unreciprocated, and the discovery of another secret Iranian nuclear site near Qom, did help build a stronger international coalition against Iran. The U.N. Security Council resolution is always the lowest common denominator, but passage of Resolution 1929 in 2010 provided a diplomatic rationale for other key players, such as the European Union, Japan and Australia, to pass even tougher sanctions on their own. Indeed, the template for the E.U. sanctions were ideas that could not pass muster with the Russians and Chinese at the United Nations.

2. Not all actions are spelled out. As part of the U.N. sanctions, Russia won an exemption that would have permitted an $800 million sale of S-300 air defense missiles to Iran. But then Russia canceled the sale anyway, in what can only be viewed as the outcome of successful, quiet diplomacy.

3. Consequences are sometimes difficult to predict. The Obama administration’s willingness to pursue a deal to supply fuel to an Iranian research reactor helped convince Russia and China that it was serious about a negotiated end to the standoff. But bungled diplomacy and miscommunication on this issue with Brazil and Turkey led to the loss of a unanimous vote at the Security Council.

4. Congressional action can sometimes be a useful tool for diplomacy, but it can also be an irritant. All administrations try to preserve as much flexibility as possible; no one likes to have their hands tied. George W. Bush was especially aggressive about adding signing statements, saying he would not be bound by some of the terms of legislation passed by Congress.