It's a group of cells on a plate? What is there here that would be illegal? This isn't any different than growing some rat intestinal lining cells in a petri dish.
but to answer your question honestly the supplier keeps stock of them by growing them and storing them. The original cells came from donations.
You could always extract some cells from a biopsy as well, but these guys likely just bought them from sigma or whatever the Australian lab-supply monopoly is.