The defence’s appeal centred on a claim of royal immunity.
Defence lawyer Marc Labelle drew his argument from an old and little-used common-law principle that states "the Queen can do no wrong."
The trial of 73-year-old Thibault will go forward now that the appeal has been denied.
In September 2009, the former lieutenant-governor was accused of misspending public money during the decade she was in office. She pleaded not guilty to two counts each of breach of trust, fraud and creating false or counterfeit documents.
As is common practice, Canada’s top court gave no reasons for its refusal to hear the appeal.
Thibault's trial is scheduled to begin in April 2014.Suggest a correction