Listening to the interview the coach did, it sounds like the reason he wasn't released is because they couldn't find a resolution with Power's academic department for the courses he takes. It sounds like his class times conflicted with the times that Canada would be practicing each day. People might point to Newhook or Holloway, but the coach explained why their situations are different. They are sophomores, and get to pick their schedule. It's a lot more flexible academically. Power is in his first semester, so the courses he takes are not very flexible, at all. Maybe the faculty at Levi's school are a little more flexible than at Power's, but Northeastern did say they should release him back if its clear he won't be a top 2 goalie.
It also sounds like Power was part of the decision, so I wouldn't be crying foul. If the kid wanted to go, he could've withdrew from the University, and showed up in the OHL in February. That wasn't what he wanted. The topic of Michigan's hockey barely came up the whole interview. It seems pretty clear this isn't a decision that has much to do with Michigan not wanting to lose a good player.
The coach said he'll be available to leave on December 10, the same day American players are eligible to leave. I know some think that American players would be released earlier, but it doesn't seem like it from what the coach said. Maybe those players have very different academic schedules than Power, but its all hypothetical and irrelevant.
Hockey Canada has to take some blame. It sounds like they aren't sure they want to invite him to take part on December 10. Why does he need to take part in this meaningless camp? The coach said he'll be released for the tournament. If Hockey Canada wants him on the team, he'll be on the team. They've potentially put him in a situation where he has to choose between the WJC and staying at Michigan. I don't see why they can't make an exception. It seems like they are purposely putting him in a bad situation. It'd be one thing if he wasn't going to be invited to the camp, but they should be working with their players to find a resolution, not telling them they either comply with their demands or they might be eliminated from consideration to make the team.