Only if the pamphlet broke the law.

I was guessing but as it stands (and it keeps evolving) it's only legal to leave your home for a few valid reasons. Eg to go to work, to go shopping, to exercise etc

To fly a plane carrying a banner isn't likely covered under any of them. Neither to be fair is protesting. However on another site I discuss politics on someone suggested the pilot etc were probably paid to carry the banner in which case that would be covered.