Sure. I would make two or three related points.
First, there are very few people who would advance the argument that sanctions alone will solve any particular foreign policy crisis. To take Iran, which is the most I think poignant recent example, sanctions there I think were designed to generate leverage that would ultimately be used in a course of diplomatic negotiations. I think very few people had the self-understanding that we could just sanction Iran into compliance with our desires about its nuclear program. Again, the sanctions were built up over a long period of time and involved broad multilateral efforts, but ultimately it was diplomacy that caused the nuclear agreement to materialize. It was not sanctions alone.
Let me abstract away from that specific example to a more general point that I alluded to, which is that sanctions are a tool of risk management. There, I think the key is that the international financial system relies fundamentally on trust. Individuals will not engage in trusted transactions with the international financial system if they believe the banks and others with whom they interact are doing business with rogue actors.
If you envision a world in which governments—particularly western governments and Asian governments—that harness the bulk of the world's financial activity simply stopped enforcing financial sanctions, which is to say, if they allowed with impunity those involved in acts like terrorism and narco-trafficking and WMD proliferation to have free access to the international financial system, I can't imagine that would be an international financial system in which trust and the free flow of information and financial services would be enhanced.
I can develop more points if you'd like, but those are the two I would make: one, sanctions are always used in complement with other national security tools, such as diplomacy, the use or threat of military force, and intelligence means, to achieve particular goals; and, second, it is very important to focus on the broad systemic effects on financial integrity when thinking about the utility of sanctions.