As with ATM cards at banks- libraries can simply institute a system where cards must be swiped to enter. This, keeping those too "intoxicated" from entering. I'd rather focus on ways to keep addicts out of these safe spaces than running the risk of a child being exposed to trauma in a public facility. I KNOW some will see this elevation in security as a blocking out or fortressing of public space but it is far more important to protect first than to react. Also to the question of how do none library members get access to cards.....simple...register online...your library card comes in the mail. Swipe. Enter.