they do get pretty cold when used in a slushie. they make your lips feel chapped or a minor burning feeling.  not enough to stop me but maybe not a good idea for cold environments.  but a metal straw is useful, and can take my abuse much better than plastic. i had not thought of the illegal usages.  
_________________________
Jim
Do you know where your towel is? 
Don't Panic! 
I have an extra.