ASP batons might be legal to carry in Boston.
1. Never carry anything you can't explain away ie: brass knuckles, double edged knives etc.
2. KNOW THE LAW AND WHAT TO SAY TO THE POLICE
3. Look into Lee Morrison from the UK for some insights, he operates under a more restrictive set of laws and has some good info.
4. Situational Awareness
5. As a final note look into a carabiner to amplify any gross motor hand strikes. Not the little ones for keys but one that wraps around your hand and is sold in outdor stores