JOIN + Subselect over M:N table
Why don't you just omit the WHERE... clause altogether? And then just JOIN all relevant tables as in:

SELECT * FROM Product
    LEFT JOIN Packaging
        ON Product.PackagingID = Packaging.ID
    LEFT JOIN LabelsForPackaging 
        ON LabelsForPackaging.PackagingID = Packaging.ID
    INNER JOIN Label
        ON LabelsForPackaging.LabelID = Label.ID