Firearms are already restricted. If you have a felony on your record you cannot legally buy a gun in the US. If you were convicted of narcotic use, protection order filed against you and so on. How many more restrictions are needed?
Restricting access to firearms for mental health reasons are necessary for everyone’s safety. Due process may seem to be taking a hit but there is a way after weapons have been seized for the person to show cause. And when proper cause is demonstrated the weapons are returned. The process by which weapons are seized is what needs to be remedied. Simply taking the word of a disgruntled ex wife doesn’t cut it.