That’s what it looks like the Australians have been doing with their gun buy-back program:

Although furious licensed gun-owners said the laws would have no impact because criminals would not hand in their guns, Mr Howard and others predicted the removal of so many guns from the community, and new laws making it harder to buy and keep guns, would lead to a reduction in all types of gun-related deaths.

…Politicians had assumed tighter gun laws would cut off the supply of guns to would-be criminals and that homicide rates would fall as a result, the study said. But more than 90 per cent of firearms used to commit homicide were not registered, their users were not licensed and they had been unaffected by the firearms agreement.

Yes, politicians assume all kinds of idiotic things.