>>42255239They'd never be able to.
Additionally they probably know, as the franchise with the most porn of it on the planet, that taking legal action against such a large group would result either in massive fan backlash or even MORE porn in protest.
Additionally, GF knows they arent what brings in yen, it's the fandom mindlessly consuming their merchandise. They want the fandom as large as possible to make the profit they do.
Because they are so large, it's actually better from a business standpoint to just say fuck it and let the fandom do their thing. They gain absolutly nothing by going on a legal offensive and only risk to lose quite a bit.
This is why you don't see Disney taking action against porn of their characters. They know it exists, but all they risking taking action against it is putting a greater spotlight on it and/or potentiality losing fans/money.