• The NICS is the FBI's background check for gun-buyers.a weapon image by timur1970 from Fotolia.com
  
  Under the Brady Handgun Violence Prevention Act of 1993, the National Instant Criminal Background Check System (NICS) was established by the Federal Bureau of Investigation (FBI) to conduct background checks on gun buyers. Under federal law and often in conjunction with state laws, many categories of people are barred from possessing firearms or ammunition.
  
  

Criminals

• Under federal regulations, it is illegal to possess firearms or ammunition if you have been convicted of a crime punishable by more than a year in prison, with the exception of state convictions for misdemeanors punishable by two years or less in prison. No one convicted of a domestic violence misdemeanor may possess a gun or ammo. Furthermore, no fugitive from justice or illegally undocumented immigrant is allowed to possess a gun or ammo.
  
  

Age Limit

• To purchase a rifle or shotgun, you must be at least 18 years of age. To purchase a handgun or any other kind of gun, you must be at least 21 years of age.
  
  

Mentally Ill

• Those who are legally considered mentally defective or have in any way been committed to a mental institution cannot possess firearms or ammunition.
  
  

Restraining Orders

• You may not own a gun or ammunition if you have been issued a restraining order by a court against harassing, stalking or in any way threatening an intimate partner.
  
  

Military and Citizenship

• Those who have been dishonorably discharged from the military may not possess guns or ammo, as have people who have renounced their U.S. citizenship.
  
  

Drug Users

• People who illegally use controlled substances are forbidden from possessing firearms or ammunition.