“Why aren’t we talking this week about bringing this Congress together on an issue like making sure that individuals who are on the terrorist watch list can’t buy guns?” Connecticut senator Chris Murphy asked that question shortly before he filibustered for gun control measures on June 15. A few days before, Omar Mateen, an ISIS gunman, had killed 49 people and wounded 53 more in a gay nightclub in Orlando.

Keeping guns from terrorists isn’t controversial, but how you go about keeping guns out of the hands of terrorists matters a great deal. Murphy was invoking a 2015 proposal by Senator Dianne Feinstein that amounted to a blanket ban on gun purchases for those on the terror watch list. Democrats unsuccessfully rallied around Feinstein’s amendment following the San Bernardino terror attack in December, and the problems with it are considerable.