All I can tell you is - I was part of a rally at the beginning of Feb. Our support truck had several 100Kgs of aid (toys, medical supplies) to deliver in Mali. Driver had serious problems getting in to Morocco from Spain. He was turned down twice, on the 3rd day a more tolerant border guard finally let him through. They suspected him of wanting to sell the goods in Morocco and wanted him to pay taxes.
Not sure about the details and paperwork involved, I was not there at the time, just heard the story second hand.