Although it is not particularly libertarian, I would agree with a passport requirement to send money to a foreign country as a feature of national security. Foreigners in America can of course use these services, but they will be subject to check for a valid VISA, either visitor, green card, or citizen. Anyone with expired VISA or “undocumented” gets reported.
libertarians are crazy. Just listen to Levin for 30 seconds if you can make it that long.