On Friday, San Francisco became the first American city to ban smokeless tobacco—chewing tobacco and “moist inhalable snuff”—at sports venues.

The new ordinance, signed by Mayor Ed Lee, goes into effect on Jan. 1, 2016. Violators will be asked to leave the playing fields (where cigarette and cigar smoking is already banned), the Associated Press reports.

Anti-smoking groups argue that a ban on smokeless tobacco—which has been linked to cancer and nicotine addiction—sends the right message to kids who look up to the players. But San Francisco Giants pitcher Matt Cain said the measure may be hard to enforce, noting that coffee pouches resemble tobacco pouches, according to an article on the team’s website.

The state Assembly is still considering a bill banning tobacco use—electronic cigarettes included—wherever there’s a baseball game, the AP reports.

Read next: Why Lawmakers Want Smokeless Tobacco Thrown Out of the Homes of a National Pastime

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Write to Olivia B. Waxman at olivia.waxman@time.com.