The Super-human Registration Act was a bill the Civil War arc revolved around. It deals with sacrificing civil liberties to promote a nation's safety.
The SHRA draws many parallels to the United States today, it purposely is very similar to the Patriot Act. However, Civil War soon branches off and it shows how all of the characters deal with the SHRA.
The bill took affect after a televised battle between the New Warriors and a group of supervillians in Stamford, Connecticut. During this battle, the supervillian Nitro causes his own body to explode, killing all of the New Warriors (with the exception of Speedball) as well as 600 other Stamford residents including sixty children at a nearby elementary school. This caused America to truly fear meta-humans and wished for them to be controlled. The SHRA was America's response. The Super-human Registration Act was passed one week after it was thought up.
The SHRA requires all meta-humans who wish to employ their powers to register with SHIELD. They must hand over all personal information to SHIELD, but it is not necessary for them to do such to the public (although Spider-Man and Iron-Man, two key supports, did give away their secret identity to the public).
Those who are in discord with the SHRA are detained by SHIELD, or heroes in cohort with SHIELD, and then put into a jail specifically for super-humans.
It should be noted that Captain America is highly against this bill, finding it a breech of the civil liberties that America stands for, and for that, he was arrested and assassinated.
This act led the way for the creation of the 50 State Initiative (an organization that will place a team of registered super-humans in each of America's states) and Camp Hammond (a ''boot camp'' of sorts for registered super-humans who have no combat training).
As of the conclusion to Siege, Captain America gave the President of the United States a list with his demands on it. One of the demands was to get rid of the Super-Human Registration Act, which the President agreed to.