We can disarm most police by fiat: police departments do not have a Constitutional right to bear arms on the job, and could be compelled to follow a new General Order that limited their access to firearms.
We cannot disarm the population by fiat, because the Supreme Court has held that the 2nd Amendment provides an individual right to bear firearms. Changing that would require radically altering either the composition of the Supreme Court, or the text of the Constitution.
Again, the question isn't whether reducing the number of guns would improve things. I'm confident it would! I don't like guns and would support the modification of the 2nd Amendment (if modifying the Constitution weren't so dangerous).
The problem is, in the United States, you can't reduce the number of guns in civilian hands. But you can reduce the number of guns in the hands of the police. Strange, but true.
We cannot disarm the population by fiat, because the Supreme Court has held that the 2nd Amendment provides an individual right to bear firearms. Changing that would require radically altering either the composition of the Supreme Court, or the text of the Constitution.