The killing of nine people in Munich on Friday night immediately triggered new debates about Germany's gun laws, but even in the midst of inevitable demands for action, Germany's politicians seemed slightly at a loss to say how the laws could possibly be any tighter.

Interior Minister Thomas de Maiziere was among the first to make new promises. "Our weapons laws are already very strong - and I think that's right," he told the "Bild am Sonntag" newspaper on Sunday. "First we have to investigate further how the suspected perpetrator from Munich got hold of the weapon. Then we must assess very carefully how and if necessary where there is still a need for legal action."

But experts agree that there is little that can be done on that front: "Germany has the strictest gun law in Europe," said Hans Scholzen, a lawyer specializing in weapons law, who pointed out that laws in Germany had been tightened following school shootings in Erfurt in 2002 and Winnenden in 2009. "If you take Belgium, or the Netherlands, or Switzerland, anyone of legal age without a criminal record can buy a firearm."

A gun's fingerprint

Indeed, reports about the 9-mm handgun used by gunman Ali David S. at the Olympia shopping mall illustrate how difficult it is to buy a gun in Germany. In a press conference on Sunday, Robert Heimberger, president of the Bavarian state police, presented the complicated history of the gun as the police have reconstructed it so far: the gun, made by the Austrian company Glock, had a Slovakian proof test stamp dated 2014, which showed it had been deactivated - that is, unable to fire ammunition.

"That stamp is like a passport, like a fingerprint for registered weapons," said Sebastian Schulte, a German military and security analyst. "Every gun, whether it is for the military, police, or civilian use, has that stamp. That means that an authority had this gun in their hands and they fired it to make sure it was working properly. So that's how we know the last time it was in legal circulation - that Slovakian stamp."

Heimberger also said police had found an Internet chat suggesting that David S. had bought the gun on the so-called "darknet." "Of course you can buy anything on the darknet, including completely live firearms - of course they're more expensive," said Scholzen, adding that they simple arrive in the post. (Bavarian Interior Minister Joachim Herrmann said earlier in the weekend that David S.'s had cost "several hundred euros").

Deactivating and reactivating a gun

Deactivation standards vary across Europe, but Scholzen says no gun deactivated in Germany could ever be used again. "You'd have to take the whole thing apart, but then it'd be broken," he said. Guns deactivated in Eastern Europe, on the other hand, can often be reactivated again very easily - since in many cases deactivation merely means driving steel pins into the barrel to block it up. Unblocking it requires neither specialist tools nor specialist knowledge, though the Glock used in Munich is likely to have been reactivated before David S. bought it.

"You need a piece of steel that fits into the barrel - which has two steel blocks, like pins, that sit in the barrel ... and then you need a big hammer, and you hit it and the pins fly out," said Scholzen. "If you're brave you just can also put a cartridge in and shoot the pins out, but that can lead to splintering."

But, Scholzen explained, if the gun has been deactivated according to German standards there would also be five holes drilled into the barrel between the pins, meaning that if you pull the trigger there is no pressure in the barrel to fire any kind of bullet.

Moreover, Scholzen said there were companies in Slovakia that legally sold prop guns that could easily be reactivated - and that the federal police was already in the process of prosecuting between 600 and 700 Germans buying them illegally. "Though you have to say these buyers are often totally ignorant," he added. "They see on the Internet 'oh, I can buy a starter pistol' which is allowed in Germany, but [they don't know] that they are only legal if they have the German stamp - the weapons from abroad don't have that."

Theater prop

Sebastian Schulte, a German military and security analyst, believes that it is significant that the Munich gun is likely to have been deactivated for use in a theater, where it would have needed to have made a bang and possibly fire blanks.

Schulte also described it as "suspicious" that the gun had received its Slovakian proof stamp as recently as 2014. "It seems to have been introduced into the illegal stream in Slovakia itself," he told DW. "Given the short time frame, and this is highly speculative, but either it must have been stolen from the theater very early - or it was intended for the black market all along."

The European Union has in fact already moved to tighten the laws around prop guns, in part because one of the rifles used in the Charlie Hebdo attacks in Paris in January 2015 is thought to have been another reactivated gun from Slovakia. As of April this year, all prop guns have had to have a special deactivation certificate to show that they cannot be reactivated.

"Of course, [the new directive] won't make a difference," said Scholzen. "Because that only regulates the legal ownership, not the illegal trade."