It depends a bit. If the claim is brought at ICSID, which seems quite possible under the Canada-EU CETA, there would be an opportunity to seek annulment of an award. The annulment committee would be made up of three other arbitrators, all of whom are appointed under the authority of the president of the World Bank. They tend to take a light-touch approach in review. For example, they wouldn't correct what they would consider to be errors of law.
With ICSID, this is entirely outside of any judicial process. This is simply arbitrators. There's no opportunity for review in any court.