I kind of thought "no," but I've brought ice through security a few times this year without problems. Indeed, last weekend, I had a quart sized bag of ice tucked into a bag of food and had no problems even though the TSA went through every item in my luggage for other reasons (see contact lens thread).

Given the absence of food on most domestic flights, I often like to bring some food with me -- especially when I travel with my kids. I feel better about bringing things like cold cut sandwiches if I can keep them somewhat cool.

A couple years ago there was some joking that the TSA was ignoring physics by treating ice as a "liquid," but I don't think there was ever any actual rule issued. Does anybody know if a TSA rule on ice exists?

TSA thinks water is explosive so anything is possible!

A TSA Supervisor in STL once took a gel-pack we were using to keep some breast milk cold, saying something like "Its only allowed for medication, not infants." After the milk spoiled, several TSA folks have agreed that he was mistaken, since the web site says breast milk is in the same category as medication.

The best you can get from TSA's website is this:
So if you put some refrigerated medical item next to your food you should be golden.

Ice is just the next battle line in the War On Water.