Board Thread:Naruto Discussions/@comment-25442883-20160112162355/@comment-26369387-20160113100959

Lilyxflower wrote: I noticd something weird after watching Naruto the Last; when Sasuke was looking at the meteor in the sky, his Rinnegan was gone and he had a normal left eye. The Rinnegan is supposed to remain in the eye permanently, right?

Madara was shown to be capable of switching between Mangekyō Sharingan and Rinnegan, so I would say original owners of Rinnegan can activate and deactivate it with free will. Nagato had Rinnegan activated permanently because he had them transplanted, quite like how Kakashi couldn't deactivate his Sharingan.