The German National Socialist party adopted the sign as its emblem in 1920. Hitler describes the design in Mein Kampf and claims the final arrangement as his own: a black hooked cross on a white disc on a red field. The form is specific. It is rotated forty-five degrees so that it stands on a point rather than square, its arms bend clockwise, and in most party usage the whole figure is tilted. The German word for it is Hakenkreuz, hooked cross. That is the term German law and German usage employ, and it is not the word swastika.
What made the sign available to the party was not Asia but nineteenth-century European scholarship. Heinrich Schliemann found the figure in quantity at Hissarlik, the mound he identified as Troy, in the 1870s, and connected it to Indian occurrences and to the emerging idea of a common Aryan homeland for the speakers of the Indo-European languages. The linguistic hypothesis was real scholarship. Its conversion into a racial theory was not, and the sign travelled with the theory into German volkisch nationalism, where antisemitic organisations were already using it two decades before 1920. Bernard Mees set out this route in detail in The Science of the Swastika. The party did not take the sign from Hinduism. It took it from philologists who had taken a theory.
From 1935 it was the national flag of Germany. It was carried on the uniforms, aircraft, banners and camp gates of the state that murdered six million Jews and millions of others, and it was the sign under which that was done. This is not one meaning among several to be weighed against the rest. It is what the sign means to a great many people who will not be argued out of the association and should not be asked to be.
The legal consequences are direct. Section 86a of the German criminal code prohibits the use of symbols of unconstitutional organisations, with exemptions for art, scholarship, teaching and reporting. Austria has a comparable prohibition, and so in various forms do Latvia, Lithuania, Poland, Hungary and Brazil. In several of these jurisdictions display is prosecuted.
One consequence fell on people who had nothing to do with any of it. On 28 February 1940, at Tucson, representatives of the Navajo, Hopi, Apache and Tohono O'odham signed a proclamation renouncing the whirling log motif in their blankets, baskets, sandpaintings and clothing, on the stated ground that a symbol of friendship among their forefathers had been desecrated by another nation of peoples. Weavers gave up a design their families had used for generations. Some Native artists have taken it up again in the last decade, and the decision is argued over among them.