> Because the government can't say "hey, destroy that thing that was legal to manufacture, purchase, and own when it was manufactured."
Actually that's a totally normal way for bans to work.
If a state decides to ban a book from school libraries, the libraries don't get to keep the books on the shelves because they already had it.
The ban on ex post facto laws merely means that, if a ban on a given book is passed today a librarian can't be punished for having it on the shelves yesterday.
Grandfathering in exceptions is just politics - make a bitter pill easier to swallow for the people most impacted; delay the costs of any remediation; deal with historical/museum pieces; and simplify enforcement.
Actually that's a totally normal way for bans to work.
If a state decides to ban a book from school libraries, the libraries don't get to keep the books on the shelves because they already had it.
The ban on ex post facto laws merely means that, if a ban on a given book is passed today a librarian can't be punished for having it on the shelves yesterday.
Grandfathering in exceptions is just politics - make a bitter pill easier to swallow for the people most impacted; delay the costs of any remediation; deal with historical/museum pieces; and simplify enforcement.