Actually there is law in anarchy. You aren't able to violate another person's civil rights which makes it illegal and only laws can do this. Where the hell did the "You can't be an anarchist if you have a flag" theory come from? Anarchists use those flags to show who we are and what we stand for. There's nothing in any anarchist theory that you can't have a flag.
And as for Che being a symbol for anarchists, he is used because he was a revolutionary who fought against the system just as anarchists do, just as communists do.
There were two “Reigns of Terror,” if we would but remember it and consider it; the one wrought murder in hot passion, the other in heartless cold blood; the one lasted mere months, the other had lasted a thousand years; the one inflicted death upon ten thousand persons, the other upon a hundred millions; but our shudders are all for the “horrors” of the minor Terror, the momentary Terror, so to speak; whereas, what is the horror of swift death by the axe, compared with lifelong death from hunger, cold, insult, cruelty, and heart-break? What is swift death by lightning compared with death by slow fire at the stake? A city cemetery could contain the coffins filled by that brief Terror which we have all been so diligently taught to shiver at and mourn over; but all France could hardly contain the coffins filled by that older and real Terror... --- Mark Twain