As written and understood currently, you cannot ban guns. They are protected by the 2nd amendment and even many leftist constitutional lawyers have agreed that the intent of the militia clause referred to the people.
But the thing the left really needs to understand is that the basic principle of justice is that you punish people who commit crimes, not innocent people. There are millions of innocent, law-abiding gun owners who aren't hurting anyone. They educate themselves on a set of laws designed (in many states) to discourage gun ownership, buy, own, and use these gun legally and safely. Some do it to hunt, some to sport shoot, some to collect, some for personal or home defense.
Why do those people deserve to be punished for the crimes of people who use guns illegally, namely to hurt people? Hurting people is already illegal. Further, the ATF has long published statistics showing that the VAST majority of guns used in crimes are acquired illegally, usually though straw purchases or corrupt firearms dealers who ignore the law. However, cracking down on these two sources of gun has never been a priority for law enforcement, not locally, nor at the federal level. If the ATF or others cracked down on these sources, the number of illegal guns in circulation would plummet.
The left's obsession with banning 'scary' looking guns or with closing the "gun show loophole" which isn't even a gun show loophole, but rather a private seller loophole through which ATF statistics tell us almost NO guns that will be used in crimes ever go through, is just a political stage show designed to impress a bunch of people who refuse to take the time to educate themselves on the topic.
Now, I am in fact NOT a gun owner, but I think we should focus on the ALREADY ILLEGAL methods by which we know most guns used in crimes will come from. And stop hassling a bunch of innocent, law-abiding people. But that will never happen because such things don't win elections.