Thank you for your question.
Compressed gas cylinders are regulated in Canada by the Transportation of Dangerous Goods Regulations which require cylinders to be manufactured in accordance with the National Standard of Canada CAN/CSA-B339, "Cylinders, Spheres and Tubes for the Transportation of Dangerous Goods". Cylinders manufactured to CSA B339 would be marked with the letters "TC" followed by the specification designation and service pressure in bar.
Cylinders that are not manufactured to a specification described in CSA B339 may not be used in Canada to transport dangerous goods including compressed gases. Such cylinders may not be modified or marked to meet a TC specification. A paintball cylinder that is not manufactured to a TC specification may not be used in Canada and there are no provisions which would otherwise allow it to be used.
Please do not hesitate to contact me should you have any other questions.
Dangerous Goods Transport Containers Engineer
Ingénieur, contenants pour transport des marchandises dangereuses
tel: (613) 990-1169, facsimile | télécopieur: (613) 993-5925
email | courriel: firstname.lastname@example.org
Transport Dangerous Goods | Transport des marchandises dangereuses
Transport Canada | Transports Canada
Place de Ville (ASDD), Tower C, Ottawa, Ontario K1A 0N5
Should a border guard be aware of this I would expect that your tank could be confiscated as unsafe. All the contact info is there should you need to get more info from them.
All we need now is someone to post something similar from DOT.