A throw-away over the line.

Keith Earls of Ireland kicks the ball a long way down the field with Geordan Murphy chasing after the ball. Under pressure Lee Byrne, the Welsh fullback, bends low to get the ball near the touch-line. He then dives into touch with Murphy in close attendance. Byrne then throws the ball further into touch.

The referee penalises Byrne.

Why?

Law 19.2 (i) If a player carrying the ball is forced into touch, that player must release the ball to an opposition player so that there can be a quick throw-in.
Sanction: Penalty kick on 15-metre line

Byrne realised that the clever Irish could take a quick throw-in and attack. The laws want players to play quickly. He prevented that. He did so intentionally. He was penalised.