Two of the activists are accused of taking part in an attack on a group of journalists covering a protest earlier this year and the seven others are being investigated for breaking into the offices of a company working on the project.
Four more anti-rail link activists have been banned from living in Turin.
The long-delayed project has been agreed by the Italian and French governments and is scheduled for completion in 2023. It has become a major flashpoint for the anti-government protest movement in Italy in recent years.
Opponents of the project plan to protest during a Franco-Italian summit next week in Lyon, where French President François Hollande and Italian Prime Minister Mario Monti are expected to discuss the issue.