Bush signed The National Instant Check System Improvement Amendments Act of 2007 -- legislation that drew support from both the National Rifle Association and gun-control groups -- late Tuesday.

The bill amends the law named after former White House Press Secretary James Brady, who was shot in the head during a 1981 assassination attempt on President Ronald Reagan. It was introduced in June by Rep. Carolyn McCarthy, D-N.Y.

It adds an estimated 2 million felons and mentally ill people to the federal background database used to check gun buyers, The Los Angeles Times reported.

The legislation came largely in response to a massacre in April at Virginia Tech, in which a mentally ill student killed 32 people before committing suicide.

"The Virginia Tech killer was able to arm himself because the court order that should have blocked his gun purchases was not entered in the Brady background check system," said Paul Helmke, president of the Brady Campaign to Prevent Gun Violence. "This new law will help ensure that records like that don't fall through the cracks."