You are right, it isn't. The situation is complex though. After WWII the Bavarian state claimed copyrights of "Mein Kampf" as Hitler was registered as a Munich citizen. Based on this copyright, publishers were not allowed to print and import it. Sales of books printed before 1945 were still allowed, based on a ruling of the German supreme court. The copyrights have lapsed recently, so technically, the book can be printed and traded again in Germany, as long as you are not using it to promote otherwise illegal activities, like exhibiting the Swatiska as a political symbol. Also, it has been put on the index, this means, you cannot publically advertise it and sell it to underage persons.

In the meantime, the Bavarian state has brought it to market again in a commented form. The original text is reproduced together with comments on the text. This issue is freely traded and even used in historical education at schools.