Yes, there absolutely should be rules. These types of relationships should be transparent. The Stanford-Lancet Commission urged the same thing.
In fact, when they assessed the roots of the North American opioid crisis in Canada and the U.S., the first area they highlighted was conflicts of interest and the movement—and Dr. Kendall, unfortunately, illustrates this—of people from roles in senior public health and governance roles into, in his case, the BCCSU, and then also into roles with other organizations like the BC Centre for Disease Control, which has been flagged as a source of funding for the very company that he and Dr. Schechter started.
It's one thing to consider whether the action of moving into pharmaceutical provision of drugs is a sensible thing. It's quite another to be advocating for that and setting oneself up to be the provider, so yes, there should be transparency.