Why can't you use karate outside of karate school?

Answer 1

You can, but only in the act of avoiding serious harm to yourself or one who is under attack.

To better understand some of the ideas that define karate, you might want to read a book called "The Twenty guiding principles of Karate" by Gichin Funakoshi (translated by John Teramoto).

The second and third principles (chapters) of this book are titled "There is no first strike in karate" and "Karate stands on the side of justice". These words alone are enough to give you your answer.

Answer 2

Karate is not to be used unless one is in danger of being hurt. Nothing will get you thrown out of my classes faster then to be discovered using the skills on others without reason.