Were they aware it existed? Did they get advice about what it meant? Did their life experiences inform them that their behavior was criminal ?

Void-for-vagueness doctrine

The phrase “consisting of two or more persons” is all that purports to define “gang.” The meanings of that word indicated in dictionaries and in historical and sociological writings are numerous and varied. Nor is the meaning derivable from the common law, for neither in that field nor anywhere in the language of the law is there definition of the word. Our attention has not been called to, and we are unable to find, any other statute attempting to make it criminal to be a member of a “gang.”
Notice that the answer to the question, “What’s fair notice ?” in vague laws isn’t subjective; that is, it’s not what a particular defendant actually knows about the law. For example, the Court didn’t ask what Lanzetta and his cohorts knew about the gangster ordinance: Were they aware it existed?
Did they get advice about what it meant? Did their life experiences inform them that their behavior was criminal ?