mlb prohibits smokeless tobacco use (like chew or dip) for all new players since 2016, and no player can carry a visible tin or package on the field or in the dugout once fans arrive.
grandfathered players face restrictions in tobacco-free stadiums (over half of them are fully banned due to local laws).
mlb player tobacco policy
https://img.mlbstatic.com/mlb-images/image/upload/mlb/oznj33evybsqmqqrxw9s.pdf
tobaccofreebaseball.org
https://tobaccofreebaseball.org/tobacco-free-stadiums/