1st....gun registration is used to later confiscate guns....the British, Australians and Germans registered guns and then years later confiscated guns.... 2nd.... actual criminals do not have to register their illegal guns.....the Supreme Court ruled in Haynes v. United States that criminals who had illegal guns did not have to register them because it would violate their Right against self incrimination.......and as for mass shooters....all 3 of the shooters you mentioned...would simply register their guns.....making registering guns pointless.....also...... Canada tried to register guns...this is what happened...... Canada Tried Registering Long Guns -- And Gave Up 15 million guns.....1 billion dollars...and it didn't work....we have 400 million guns...... The law passed and starting in 1998 Canadians were required to have a license to own firearms and register their weapons with the government. According to Canadian researcher (and gun enthusiast) Gary Mauser, the Canada Firearms Center quickly rose to 600 employees and the cost of the effort climbed past $600 million. In 2002 Canada’s auditor general released a report saying initial cost estimates of $2 million (Canadian) had increased to $1 billion as the government tried to register the estimated 15 million guns owned by Canada’s 34 million residents. The registry was plagued with complications like duplicate serial numbers and millions of incomplete records, Mauser reports. One person managed to register a soldering gun, demonstrating the lack of precise standards. And overshadowing the effort was the suspicion of misplaced effort: Pistols were used in 66% of gun homicides in 2011, yet they represent about 6% of the guns in Canada. Legal long guns were used in 11% of killings that year, according to Statistics Canada, while illegal weapons like sawed-off shotguns and machine guns, which by definition cannot be registered, were used in another 12%. So the government was spending the bulk of its money — about $17 million of the Firearms Center’s $82 million annual budget — trying to register long guns when the statistics showed they weren’t the problem. There was also the question of how registering guns was supposed to reduce crime and suicide in the first place. From 1997 to 2005, only 13% of the guns used in homicides were registered. Police studies in Canada estimated that 2-16% of guns used in crimes were stolen from legal owners and thus potentially in the registry. The bulk of the guns, Canadian officials concluded, were unregistered weapons imported illegally from the U.S. by criminal gangs. Finally in 2011, conservatives led by Canadian Prime Minister Stephen Harper voted to abolish the long-gun registry and destroy all its records. Liberals argued the law had contributed to the decline in gun homicides since it was passed. But Mauser notes that gun homicides have actually been rising in recent years, from 151 in 1999 to 173 in 2009, as violent criminal gangs use guns in their drug turf wars and other disputes. As in the U.S., most gun homicides in Canada are committed by young males, many of them with criminal records. In the majority of homicides involving young males, the victim and the killer are know each other.