Don't quote me on this, but I would imagine you can as long as they have no resin in them. So basically don't use them. They might get pulled out of your luggage and checked out, but as long as they're crystal clean, I would think it'd be okay. That's how head shops get away with it here, as far as I know. "It's a tobacco pipe, maaaan!"
my cousin brought two bongs with him from San Diego to where Im at an they didn't say shit, then agian, he brought weed with him on the plane also.