The NHL/CHL (Canadian Hockey League) partnership is something fans tend to talk about during this time of year, but much of what people believe they know about the agreement is myth. It's easy to see why, because the arrangement between the two leagues isn't covered in the NHL's Collective Bargaining Agreement, (the basic contract between the National Hockey League, team owners, and the NHL Players Association), which any fan can access online. One huge myth going around the internet is that the American Hockey League has an age limit, which would obviously place restrictions on entry. The truth is, like the NHL, there is no age limit for the AHL; league policy is that any player over the age of 18 can play in the American Hockey League. So why won't players such as Jonathan Huberdeau or Erik Gudbranson be seen in San Antonio this season?
Players will often play two more years in the CHL after being drafted, with exceptions to players born between September 15th and December 31st (Nazem Kadri last season), or players who are talented enough to make the team out of camp (Taylor Hall and Jeff Skinner). The players born in the fall are often the oldest in their draft class, and usually play only one more season before crossing over the pros.
There are still ways a junior-eligible player can play in the AHL. CHL seasons usually end in the final months of the NHL and AHL seasons, and once a player's season is finished, if they're signed by their NHL club, they can play in any minor league late into the year, and be returned to their CHL team the next season. The other is the ten-game rule: any junior-eligible player can play ten games in the NHL (or AHL) without it counting on the player's entry-level contract and it does not count toward the team's 50-contract limit. An example is Jared Cowen, who played one NHL game with the Ottawa Senators in 2009-10 without counting towards his contract, and joined the Binghamton Senators in the playoffs last season during their Calder Cup winning playoff run.
Players drafted from European and NCAA leagues aren't held to these terms, but players drafted out of Europe by a CHL team are. A player's nationality doesn't matter; the team that drafted him first does.