Officials at the Kingston Penitentiary told the Star last week all the letters mailed July 27 were being returned because of federal laws that prohibit revealing the location of inmates within the correctional system.
The questions were about the quality of life in the prison in southeastern Ontario that was opened in 1835, the Star said.
Unlike the United States, the location of inmates across the country isn't public information, although in high-profile cases such as those of serial killers, the information is widely known from media coverage of the trials.
Correctional Service Canada policy states prisoners and senders must be "promptly" informed when mail is intercepted and returned, the newspaper said, questioning why it took eight weeks for the Star to be told of the interception. The newspaper said it had chosen not to follow guidelines in which a prison official must approve a media interview along with an inmate's written consent.
Professor Kent Roach of the University of Toronto Faculty of Law said he found the prison's mail denial unfair.
"I think it's very important for people to understand that, first, prisoners are people and second, they don't have access to the outside world except through mail and the telephone," he said. "So restrictions of this kind, I think, would have a very severe impact on prisoners."