Is it legal to ship someone using a controlled atmoshere shipping container?
They would have various amenities (food, water, entertainment etc) And they will be shipped from Canada to Spain.
Well, it depends.
I am personally aware of 2 engineers who were housed in a shipping container during sea trials of the Royal Australian Navy's HMAS Success. This was carried out with the knowledge, permission and active participation of the navy and was perfectly legal.
However, if these people were smuggled onto a ship that would be illegal.