Mein Kampf has never been banned from possession in Germany. It just has not been published in the post-WW2 decades because the copyright holder, the Free State of Bavaria, decided to just not publish it and withhold the right to do so from anybody else. One could readily purchase, sell, or trade old copies at an antiquarian bookstore.
It's now in the public domain, so one could even set up a little publishing company and publish it oneself.
And it's an incredibly awful book, measured to all the 'fame' it holds in certain circles.