How about loans to European teams?
That's not a CHL thing and has nothing to do with the NHL-CHL Agreement.
That is part of the CBA negotiated between the NHL and the NHLPA:
Section 8.7
8.7 Age 18 and 19 Players. (a) During the first two seasons next succeeding the draft of an age 18 Player, the Club he signs an SPC with
must first offer him to the club from which he was claimed before it may Loan him.
The PA wanted protection for its membership by preventing 18 and 19 year old player influx and "taking away other player's jobs." The NHL gave into the PA demands and countered with they can't be loaned anywhere, hence the player must be offered to the team he was drafted from first.
In this case, the Guelph Storm could say they don't want him back (why would they?) and the Bruins can place him anywhere in the world they want. It's the same thing with players drafted out of the USHL that has almost identical age restrictions on its players as the CHL.
Players drafted out of Europe have always been allowed to go to the AHL immediately. But there's a new agreement between the NHL and some European leagues that will allow those countries to keep players there for a minimum of 4 years.
Player movement is not easy. There are plenty of negotiated deals between the NHL, PA, Hockey Federations, IIHF and other leagues. And everyone of those leagues/federations allows their players to go back if they so choose (or the NHL team chooses). The only league in the world that has a rule against it is the NCAA.