The similarity between the two games has meant that players can switch between the two codes. League initially recruited big name players from union, like Herbert "Dally" Messenger in 1907, and the RFU responded by banning any player that played rugby league for life.
The similarity between the two codes has resulted in players being able to switch between them. The Rugby Football Union (RFU) responded by banning any player who had played rugby league, following the recruitment of prominent players from the union.