(It is illegal to bring Freon Canisters across the border)....The CBP released a reminder. Bringing Freon Canisters into the United States from Mexico could result in fines and or vehicle seizure.

CBP says the importation of Freon is restricted and must adhere to strict federal commercial importation requirements. If you are caught with undeclared Freon canisters in a passenger vehicle may result in fines, and you could even lose your vehicle. Depending on circumstances, you could also face federal prosecution.