The International Ice Hockey Federation reviewed a minor penalty to Reinhart for high-sticking U.S. forward Vince Trocheck in Thursday's semifinal and handed down supplementary discipline Friday after a hearing.
The Edmonton Oil Kings defenceman will miss Saturday's bronze-medal game against Russia. Reinhart must serve the remaining three games at his next IIHF event, which would be the next world junior championship.
Hockey Canada is appealing the suspension believed to be the longest in the tournament's history.
Reinhart, 18, is eligible to play for Canada again in 2014. The Canadian team will want his experience in their lineup in Malmo, Sweden.
What's more, should Reinhart play for the NHL's New York Islanders next season, the Islanders might not want to make Reinhart available to the Canadian team if he has to sit out three games.
"Especially playing against Russia tomorrow, I wanted to be a part of that game, the last game of the tournament, so it's really devastating for me," Reinhart said Friday after practice at Ufa Arena.
"That leads into next year too if I get the opportunity to play. I'd be a big part of next year's team hopefully and to be out for some of that as well, that's definitely a big loss."
Reinhart was guilty of carelessness with his stick and was lucky he didn't receive a double minor in the second period Thursday. But he didn't appear to deliberately swing his stick at Trochek's helmet.
"As I explained in my review today, as I was tripping I kind of lost balance and my stick rode up his stick and made accidental contact to the head," Reinhart explained. "The referees on the play thought it was a two-minute penalty, a two-minute minor, and I agreed with that.
"The suspension of four games is definitely a bit of a shock to me, but (there's) nothing I can do about right now."
Reinhart, six foot four and 202 pounds, has 12 penalty minutes in 31 WHL games this season.
He's the third Canadian player to get suspended at the 2013 world junior hockey championship. Boone Jenner was suspended for three games on the eve of the tournament for a late hit during an exhibition game. JC Lipon sat out one game for getting his elbow high on a Slovak player.
Hockey Canada's senior director of hockey operations accompanied Reinhart to the morning hearing with the IIHF's disciplinary committee, comprised of former NHL referee Dan Marouelli, who is a Canadian, and Jeff Sauer of the United States.
"Griffin stated his case and said all along it was an accident, I believe it was an accident, the four officials on the ice believed it was an accident," Scott Salmond said. "There's no question in my mind we'll appeal.
"That's the harshest suspension in the history of this event."
Salmond believes the penalty is out of proportion compared to the one-game suspension given to Russian forward Valeri Nichuskin. He was given a major and a game misconduct for checking Canadian defenceman Tyler Wotherspoon from behind during their preliminary-round game.
"I fully respect the fact players have to be responsible for their actions and for their sticks," Canadian head coach Steve Spott said. "The hit we took in the Russian game on Tyler Wotherspoon, that's a deliberate act and an intent to injure.
"What Griffin Reinhart did was an accidental use of his stick. If that's a four-game suspension, I see the game completely differently than people making those decisions."
Hockey Canada's appeal will be handled at an IIHF council meeting later this month, Salmond said.
"We're trying to get some consistency and understand one game, two games, four games," he said. "All I'm asking for is some consistency."
When forward Jonathan Huberdeau was suspended for four games in the Canadian Hockey League, he served the fourth during one of Canada's pre-tournament games in Finland because the IIHF recognizes CHL suspensions.
The reverse is not true in Reinhart's case. The suspension must be served during an IIHF event, and neither CHL nor international exhibition games count towards it.
"We're not talking about just a young player who is going to serve (a suspension) in what could be one of the most important games of his life tomorrow," Salmond said. "To say he's going to serve the next three next year and not in an exhibition format, but in an IIHF championship format . . . that's a harsh penalty."