What did the Trump administration know about Friday’s “extreme vetting” executive order, and when did they know it?

This weekend’s fast-evolving controversy over the order, which bars entry into the United States for 90 days for people from seven Muslim nations, is President Donald Trump’s first substantive and serious public policy snafu. The chaos that erupted in American airports—both in the confusion about what law enforcement was expected to do with visa-holders arriving in the U.S. from those countries, and in the protests that emerged there—set the tone for how everyone processed the whole executive order. What did the order say? Who was affected by it? Was it constitutional? Was it effective? It was as if we needed a total and complete shutdown on news developments about the travel ban until we could figure out what the hell was going on.