Mayor Bloomberg of New York City is calling it Congress for failing to close a loophole in gun purchase laws. Under federal law, individuals can be blocked from legally purchasing guns and explosives. Being on the FBI’s terrorist watchlist, however, does not block a person from being able to purchase guns or explosives.
The FBI’s terrorist watchlist consists of individuals who are "known or reasonably suspected of being involved in terrorist activity." Congress, despite requests from both from both the Bush and Obama administration, have not closed that loophole. The main opposition to the bill that would close the loophole allegedly stems from the NRA, which is considered the most powerful lobbyist in Washington. The NRA complains that the bill would give too much leeway to the federal government to block individuals from purchasing arms.
NYC Mayor Bloomberg Outraged; Will Call Congress Out On ‘Terror Gap’ | The Huffington Post