Rule added to a sport by a governing authority that makes the sport more complex while trying to increase advertising revenue. The grossest violations occur in the NBA, where the zone defense is illegal, and the shot clock is a mere 24 seconds. This takes strategy out of the game, in favor of flashy moves and high scoring games.

In football, why are only designated people allowed to catch the ball? Each team has the same number of players, so if I want to sent eight of my players downfield, leaving my quarterback very exposed, why can't I? Yet, there is a rule against doing this. Oh well.

The NBA's anti-zone rule is definitely an artificial rule by joev's definition, particularly since it applies only within the realm of that league itself, and really contradicts the way the game is played in every other setting.

Conversely, I wouldn't consider American football's receiver-eligibility rules artificial, since they apply at every level of organized play (and even apply, with certain modifications, in two variants of the game, Canadian football and arena football). Closer to joev's definition would be the NHL's decision as of the 1999-2000 season to use 4-on-4 play during the five-minute overtime period in the regular season.