The interpretation that considers "packing for distribution" as an exemption and not "distribution" makes for a grammatically incorrect sentence in any case. "

The interpretation that considers "packing for distribution" as an exemption and not "distribution" makes for a grammatically incorrect sentence in any case. "A, B, C or D" is a correct sentence without Oxford comma, and the structure used originally. "A, B, C, or D" is also correct, and does have the Oxford comma. But the interpretation I mentioned reads the sentence as "A, B, C" -- where C is the whole of "packing for shipment or distribution". You need something there, either "and" or "or" or something similar. I'd say the language is perfectly unambiguous, if a little strained. But that's just law texts in general. Edit: consistency