Some eastern european salute versions had a simple stick welded into the barrel. Making the barrel shorter made the guns fully functional, so terrorists did just that.
Politicians were desperate to create an illusion of control after the paris massacre. Combine the will to symbolic political action with the absence of knowledge on guns and everything is present for more useless legislation
Someone confused these weapons with the more thoroughly modified german salute rifles and then these with the completely deactivated ones.
The result is phenomenal:
Decoration weapons now need to have their triggers welded, magazines welded and filled with epoxy resin, bolt carriers welded, bolt heads ground, barrels welded to the body, barrels drilled, barrels welded. Its a brick of steel that cannot be disassembled or used to demonstrate the function of the rifle. It lost most of its fun and educational value. Expected deaths avoided? 0 Probably someone will get hurt trying to disassemble one.
Also new regulations for live weapons. I had the pleasure of buying and moving a new heavy safe for my guns. Then there are those utterly dangerous large magazines. If you bought one (german law) before 2017, keep it. If you bought one a day too late it is a banned weapon and treated the same way as a complete assault rifle. Special permit on request, needs to be stored in a high security safe. If you don't own weapons and just the magazine and you bought it before 2017, store it on your kitchen table or whereever you like. Strictly speaking: If you have two magazines of the same type and you accidentally switch the one you are not required to store in the safe with the one you must lock there you are committing a crime.
When asked about it the parliamentarians say "We only do what the EU requires us to do" which is not true because the EU wrote nothing about the magazine thing and which becomes an outright lie considering that it was the german MEPs who started the EU firearms directive. Switzerland was forced to implement it, too. The threat was to kick them out of Schengen free trade if they said no. 36,2% of the voters would have risked free trade for keeping their gun laws. In other words: The EU forced millions of citicens of a neutral country to give up some of their rights. Fortunately the swiss are very liberal with special permits for semiautomatic rifles. The EU allows special exemptions, so almost everyone gets one.
All of this also represents compensationless devaluation of property. A good condition MP38 used to be worth as much as a car, now it cannot be sold (legally) anymore. All these pieces of history are marked for eventual destruction. Individual gun parts were legal here in germany. Only bolt head and barrel required a license. Now the receivers and triggers also count and need to be registered. Millions of individual parts are now illegal. 5 years of prison for buying a harmless brick of metal without a barrel.

As long as there are some checks for ownership (no history of violent crimes and no episodes of schizophrenia in the last 5 years) I don't mind civilians owning fully automatic rifles. Civilians are allowed to own planes and crashing a bombardier (interesting name) business jet into a crowd creates equivalent carnage. As these jets are often luxury items I don't accept the "but transportation is a legitimate use" argument. Allow the people to have some fun or build a prison state. Considering the amount of surveillance in london Britain seems to have chosen the second option. It's not just guns, even carrying knifes is now banned in many areas. The problem is that criminals just don't care. At least my gun permit allows me to carry a little knife in no-gun zones here in germany. That is about the only new law that makes sense. People with a gun license have never been sentenced for a violent crime, let them carry knives.

If I were the government, I would take a look at the used market for biomedical equipment. You can now get a lab better equipped than the soviet bioweapons program for a million euros. But nah, lets focus on imposing restrictions on legal gun owners. The illusion of security is so much easier to achieve than actual security.