It is a run out, it is Law 38.3, and it is fine

Somebody takes the bails off at the bowler's end, the non-striker was halfway down the pitch before the ball was released, and within a minute there is somebody at deep square leg explaining that it is against the spirit of the game. It comes round every year, like the covers.

The Law is short and it is not ambiguous. Here is what it says, in full, from Law 38, which is the Law called Run out.

At any time from the moment the ball comes into play until the instant when the bowler would normally have been expected to release the ball, the non-striker is liable to be Run out if he/she is out of his/her ground. In these circumstances the non-striker will be out Run out if he/she is out of his/her ground when his/her wicket is broken by the bowler throwing the ball at the stumps or by the bowler's hand holding the ball, whether or not the ball is subsequently delivered.

MCC Laws of Cricket, Law 38.3.1

The Law then defines the cut-off precisely, which is the part that gets shouted over. The moment the bowler would normally have been expected to release the ball is the moment the bowler's arm reaches the highest point of the delivery swing. Before that, the non-striker is fair game. After it, the bowler has missed the window.

The bit that settles most arguments

It sits in Law 38. Run out. It is filed with every other way of being out of your ground at the wrong moment, and it has been since the 2022 code moved it there.

It used to live in Law 41, which is Unfair play, and that placement is where the whole cultural argument came from. Go and read Law 41 now. The only mention is 41.16, batters stealing a run, and even that clause stops to point you back to Law 38.3 for this exact case. The Laws stopped calling it unfair and the boundary rope did not get the message.

So why does anyone still mind

Because it feels like a trick, and cricket is sentimental about the difference between beating someone and catching them out. That instinct is not stupid. It is just not a rule, and the batter cheating for a yard is the one who introduced the sharp practice.

A non-striker who leaves early is stealing ground on every delivery. Nobody calls that unfair, because it is invisible until somebody makes it visible. The bowler who takes the bails off is not inventing an advantage, they are ending one.

What to do about it at your club

Stay in. That is the whole answer. If you are square of the crease when the arm comes over, you are gambling that nobody in the opposition has read the Law, and that gamble gets worse every season.

If you are the bowler, do it early in the innings when it costs the other side a look rather than a match. And if you must warn them first, understand that you are being generous rather than obedient. The Law asks for no warning at all.