I haven't seen many celebrity endorsements for cannabis in general, there may be restrictions against it. The part below about university sponsored activities not permitting marijuana would lead me to believe the university would prohibit student athletes from NIL deals for it regardless
"Now that Amendment 3 has passed, will marijuana be permitted at the University of Missouri System?
No. Marijuana continues to be prohibited on the University of Missouri System’s property and at University-sponsored or University-supervised activities in accordance with federal law and University policy."
https://www.umsystem.edu/ums/gc/faqs#:~:text=May%20medical%20marijuana%20be%20used,for%20medical%20or%20recreational%20reasons.