Banksy's "No Ball Games" work appears on walls in various locations and has been documented, auctioned, and removed over the years. The image is simple: two children playing, the universal image of childhood recreation, placed against the backdrop of the prohibition sign that neighborhood councils and property managers use to ban exactly this. The text says no. The image happens anyway.
The WRPSA art series finds specific resonance in the combination with Rock Paper Scissors. The sign prohibits ball games. Rock Paper Scissors requires no ball. It requires no equipment at all: no bat, no net, no goal, no court, no minimum number of players, no physical space beyond two people's hands. The restriction doesn't apply. The game is structurally outside every regulation designed to control games, because those regulations were written with games that require something in mind.
This is one of Rock Paper Scissors' most durable properties. You cannot confiscate it. You cannot fine someone for playing it. You cannot prohibit it in a space where hands are allowed, which is all spaces where people are allowed. Every attempt to regulate games runs up against this problem: there is always the game that predates regulation, that requires nothing, that will continue to be played regardless of what the sign says.
Banksy's practice is built on the observation that public space is contested. Whoever has a surface and something to put on it makes a claim on that space. The children in the image are claiming the wall. The sign was the previous claim. The image comments on whose claim is more legitimate — the institution that banned play, or the children who need a place to play.
Rock Paper Scissors makes the same implicit argument every time it's played in a space that has rules about games.