This is a great question that I definitely don't know the answer to yet.

There is a trope around graffiti artists that their biggest fans are the police. Often an artist will spend all night painting a mural, and then by the morning its already gone, but the paint "buffers" submit a photo to the police.

I definitely think there will be a cat-and-mouse synonymous with the adversarial neural networks examples for hiding weapons in everyday objects.

At the end of the day, most street art is commissioned or done in pre-approved areas, so I don't think it will be a cause of concern with larger artists.