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Thanks, everyone, for such quick replies.

Following are excerpts of the replies I received.  Generally, while
canola (rapeseed) is GF in and of itself, it is grown in rotation with
wheat (one year wheat, next rapeseed, next wheat, etc.).  Therefore, the
possibility of cross contamination.  In addition, it contains a particle
of protein that many people seem to be sensitive to.  So while it may be
GF, some people may have a reaction due to sensitivity.  Hope this
helps!

    Because canola  or rape seed is grown in resting wheat fields and at times
    volunteer wheat plants grow up among the canola plants and then are
    harvested along with the canola, so its impossible to say that canola oil
    is uncontaminated by wheat.

    However, most people do not have a problem with it.


    The theory is that wheat is grown in fields in rotation with canola.  Some
    people feel there is a risk of contaminatin during harvest.

    As I understand it, canola is gluten-free.  It is made from rapeseed and
    contains a particle of protein (the name I can't remember and I can't find
    the source to quote) that some people are sensitive to, thus the CSA has
    listed it on the "don't eat" list.  .  .  .  .  If people react to canola
    oil it is not because of the gluten but because of sensitivity to that
    particular protein.

    Basically canola oil is derived from canola or rape crops
    primarily in Canada.  This crop sometimes is grown in fields that were
    previously wheat, therefore there is some thought of cross contamination.


    Because it is grown on wheat fields (rotation crop).  It is contaminated
    while growing.