They are banned somewhere and the library is open in Portugal.

If they were banned in Portugal it would run afoul of the legal system, and probably be closed down, obviously.

But if the criteria of being in the library - that the book be banned somewhere in the world; that's a reason to visit the library in of itself.

Though I think there's going to be a lot of garbage, one need only remember that Life of Brian (the Monty Python movie) is banned in the Vatican. (along with a bunch more).

Sometimes just seeing what is banned and where is a sort of art in of itself.