I would argue you shouldn’t even bring them inside. The amounts necessary for toxicity are insanely low…like a bit of pollen, a small clipping of the leaves or stems, a small puddle of water left behind from rinsing; all of these are potentially toxic to your kitties.

Also side note, illegal or not, cats get out / get lost. Its a bit callous to hold the cats in your neighborhood up to standards of the “law” and careless owners / accidental runaways.