Josh Snow tells Angela that they are being framed since the gun was only loaded with blanks and that "there is no way someone can die from a blank." Actually, that is not technically true. A blank cartridge's end is crimped over a plastic wadding that is used to prevent the gunpowder in the cartridge from leaking out. If someone fires a blank cartridge at another person at point-blank range, it is possible-- though extremely unlikely--that the plastic wadding could penetrate the skin and puncture or even sever a major vein or artery. That is why general guidelines regarding firing a gun loaded with blanks in another person's general direction--like an actor might when a scene calls for them to shoot another character-- state that the shooter should be a minimum of six feet away from the other person when they fire the blank. Whenever a script calls for an actor to "shoot" a fellow actor at close range, they use what is known as a "non-gun," a non-functional prop gun that cannot fire a cartridge.
Josh Snow (Aaron Stanford) the professional poker player and gambler who is the main focus of this episode is very similar to the main character of Cruise to Nowhere (2006). In that episode, a kid named Joey Frost (Lou Taylor Pucci) had been taught by his father--himself a career gambler--how to play poker and read people's tells from a very young age. Joey's father winds up getting murdered. Joey is then raised by his uncle, who uses Joey to make money by hustling poker. It turns out his uncle murdered his father, which Goren and Eames figure out. Goren takes Joey under his wing, and Joey starts to look up to Goren as a father-figure. After the case is solved, Goren encourages Joey to put his talent for playing poker to good use by going professional. In this episode, Josh Snow says that he had known Goren when he was a kid: Goren had caught the man that murdered his father, and Goren had kept in touch and had followed his professional poker career.
Permits are actually not required for antique rifles and pistols in New York City, as long as they are muzzle-loaders, they use "fixed cartridges" that are no longer commercially available, and they are meant for display only--like the Springfield percussion cap rifles Lou Cardinale has on display in his bar. Background checks are also not required for antique black-powder firearms and for modern replicas of them.