The author did let this cat out of the bag: gun registration was part of a program of gun control. “In 1928, the Reichstag relaxed the regulation a bit, but put in place a strict registration regime that required citizens to acquire separate permits to own guns, sell them or carry them.
As everyone with any knowledge of German history in the 1920s knows, the Nazis ignored this law. In 1933, they took over. They suppressed all dissent. How? Because they were armed, while the rest of the population wasn’t. Is there cause and effect here? Salon does not mention this causal sequence. It’s clearly irrelevant, assuming you are a gun control promoter along Weimar lines.