The law as written was unclear and susceptible of multiple interpretations. I personally would look first to the legislative history for guidance to resolve the ambiguity. Lacking such guidance, then since it created a set of exceptions to the usual rule, I would pick the interpretation that creates the smallest set of exceptions. The Oxford comma would not be the only way to rewrite that law to explicitly exclude delivery.
Not sliding the "the", the "of", or both would make the intent clear regardless of whether an Oxford Comma was used or not.
The below rewrite is clearly adverse to employees regardless of whether the Oxford comma is used or not used, albeit a bit clunky.
The canning of, the processing of, the preserving of, the freezing of, the drying of, the marketing of, the storing of, the packing for shipment of or the distribution of:
(1) Agricultural produce;
(2) Meat and fish products; and
(3) Perishable foods.