Most likely the .gov would instill martial law, and anyone caught out would be detained, searched and have all known associates investigated as well. However in a large city such as NY with lots of underground tunnels it would be much more successful. In a large city its much easier to evade detection while traveling by using sewer, subway and other access tunnels. The other option for a small insurgency like you describe would be to use homemade explosives on RC vehicles to deliver them to the target(s). But using your scenario martial law would be the .govs answer to containment, detainment and investigation. This would indicate anyone out after curfew or against orders as an enemy combatant and a target.