In his speech Sunday night on the San Bernardino killings, President Obama called on Congress “to make sure no one on a no-fly list is able to buy a gun.” The logic seems impeccable. The no-fly list contains the names of suspected terrorists who are not allowed to travel on airplanes. As Obama earlier said, “If you’re too dangerous to board a plane, you’re too dangerous, by definition, to buy a gun.” Yet Republicans have already rejected a proposal by Sen. Dianne Feinstein based on just this logic. Has gun-rights nuttiness run amok? Or do the Republicans have a point?

The answer is more complicated than it might appear. The no-fly list has drawn the complaints of civil libertarians since it was established after the Sept. 11 attacks. The list contains the names of people who the government thinks are a threat to civil aviation—terrorists. The government constantly updates the list and sends the names on it to airlines. These people are denied passage, often left stranded in some foreign country until they undertake the arduous process of seeking help from the local U.S. embassy. For all practical purposes, they cannot travel by air. Yet the government does not have proof that these people have committed crimes nor, since it can’t see into the future, that they will commit crimes. Thus, the no-fly list seems to violate the presumption that people are innocent until proven guilty.

Read more at Slate