Dan:

We still have it on the books in Canada (ss. 59-61).  It is defined as
"advocating the use of force as a means of accomplishing a governmental change"
(more than mere criticism).  In the last decade, some suggested that
provocations of the separatist government in Quebec were seditious (and some
likely were by historical context) but no sane person would be serious about
advancing that today.  The crime is pretty much lost to the rough and tumble
world of politics and free speech.

The last prosecution was in 1949 and unsuccessful, so it is a dead letter for
practical purposes.

Cheers,
Peter Bowal
University of Calgary