Gun Control - A "bad thing?"

Here's the basis of the Democratic stance on "Gun Control" as per their own proposal:


Limit the capacity of ammunition magazines; expand background checks to include sales at gun shows and other private transactions; and require better record keeping to keep guns out of the hands of those with mental illnesses. It would also try to curb gun sales in states with more relaxed gun laws to buyers in states with stricter laws.

One wonders: What is the criticism of the above?