In the state of Florida, If taking off your shirt reveals that you are a member of a certain race, whereas leaving your shirt on would conceal this fact, you must keep your shirt on.
Second, running shirtless makes me uncomfortable, and is therefore banned in Florida if there is a school within 500ft of your running route.
Third, if you are gay or transgender, you must keep your shirt on at all times because we don't want to groom any children.
Finally, if you are running shirtless while reading a book that has LGBTQ wording in it, you will go immediately to prison.