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Well you could limit things with robots.txt instead, but that's a bit of a blanket block. It would probably be better than nofollow though. Using noindex and nofollow in conjunction would also likely be better than just nofollow by itself. It's a long way from the elegance and usefulness of rel="canonical" but it is easier.

Hi Baptiste... yes, we failed to get him to even have one /category/ in there... I do not know why he couldn't do this.....!