The NICS Improvement Amendments Act was passed in 2007 in the wake of the Virginia Tech shootings in order to address loopholes in the National Instant Criminal Background Check System, commonly known as NICS, which enabled Seung-Hui Cho to buy firearms despite having been ruled a danger to himself by a Virginia court.
Under the Gun Control Act of 1968, it was illegal for Cho to purchase the firearms; however, the Commonwealth of Virginia had not submitted his disqualifying mental health adjudication to NICS, which failed to deny the sale.
A rule submitted by the Social Security Administration relating to the implementation of this act was repealed under the provisions of the Congressional Review Act on February 28, 2017.
References
NICS Improvement Amendments Act of 2007 Wikipedia(Text) CC BY-SA