i have never heard of warmers being illeagal, my older daughters HS team uses them in the winter time. my youngest uses one too. we live in Louisiana and pla USFA
i just read the rule book and warmers are NOT illegal, warming the bat is not altering the physical structure of the bat and we will continue to use ours untill told other
They might not be illegal in USFA, but they are illegal in other associations. I'm not a rule book guru, so I can't dig up the exact rules and all that stuff but I know they are illegal in some places.
Based on what those links, only a few of them are legal. I wonder why only certain ones are legal, while others are not. I'd also like to know what is legal for HS ball.