Under current law, someone can purchase as much as 50 pounds of explosive "black powder" without a background check, as well as an unlimited amount of "smokeless powder" and "black powder substitute."

Pressure cooker bombs were used at the finish line of the Boston Marathon (Twitter)

U.S. Senator Frank Lautenberg (D-NJ) has reintroduced legislation, in light of the recent Boston Marathon tragedy, to require that all sales of explosive powder be subject to a background check. Lautenberg said such powders can be used as the explosive material in assembling pipe bombs and pressure cooker bombs, like the ones found in Boston.

"It defies common sense that anyone, even a terrorist, can walk into a store in America and buy explosive powders without a background check or any questions asked," Lautenberg said. "Requiring a background check for an explosives permit is a small price to pay to ensure the safety of our communities."

Lautenberg introduced a similar proposal in 2003.