This may sound like a trivial distinction, but it's actually kinda important: It is
not against the law to have your face covered in public. It isn't even against the law to have it covered on private property, like a mall.
It may be against the
policy of the mall, but all they can do is ask you to uncover it, and tell you that you will be required to leave unless you uncover it. Even then, you're still not breaking the law if you refuse to uncover your face. (But you are now breaking the law against trespassing, since an agent of the property owner has told you to leave.)
Sorry for ranting; it just bugs me how often these days company policy gets mistaken for government law. Companies can frequently buy laws written the way they want, but they aren't (yet) allowed to directly set the laws.
Also, when I read the thread title I thought the topic was cosplayers getting high in public, while in costume. .
I actually thought it was cosplayers tripping people in public at first.
(Have I mentioned lately that I love you guys?)