The European Court of Human Rights ruled Thursday that insulting Islam's founder is not covered by freedom of expression.
A seven-judge panel said defaming Mohammed "goes beyond the permissible limits of an objective debate" and "could stir up prejudice and put at risk religious peace."
The decision came in the case of an Austrian national identified by the court as 'Mrs. S' for comments she made in two seminars in 2009.
The court said the woman's comments were not protected by freedom of expression because "the applicant's statements had been likely to arouse justified indignation in Muslims" and "amounted to a generalization without factual basis."
An Austrian court convicted her of insulting Islam in 2011 and fined her 480 euros. She lost two subsequent appeals.
The European Court of Human Rights ruled that Austrian courts "carefully balanced her right to freedom of expression with the right of others to have their religious feelings protected, and served the legitimate aim of preserving religious peace in Austria."