Those who violate the law will be ejected from the premises.
"Today, San Francisco entered the history books as the first city to take tobacco out of baseball," said Matthew L. Myers, president of the Campaign for Tobacco-Free Kids, in a statement issued to The Associated Press. "The home of the world champion Giants has set an example that all of Major League Baseball and the rest of the country should quickly follow."
Using smokeless tobacco is a habit among numerous players, despite its publicized health risks.
The absence of urgency in the Giants' clubhouse regarding the law may have stemmed from the fact that it won't be enforced until Jan. 1, 2016. Right-hander Matt Cain, the club's player representative, said his teammates have not discussed the matter among themselves.
"Now that [the law has] gone through, we'll definitely hear more about it," he said.
Pointing out that coffee pouches resemble tobacco pouches, Cain added, "I think the hard part will be policing it."
After considering the issue carefully, left-hander Madison Bumgarner issued a statement: "Hopefully it will be a positive thing for us players. It's not an easy thing to stop doing, but I support the city."
Manager Bruce Bochy approved of the law.
"It's a step in the right direction," he said. "I think it can be a good thing. It's going to be hard to enforce. It's a tough habit to break."
Smokeless-tobacco use has been banned in the Minor Leagues since June 15, 1993. Major Leaguers cannot be prohibited from chewing or dipping tobacco without an agreement from the Players Association.
• Infielder Matt Duffy, who replaced Casey McGehee in the lineup in the previous three games and went 5-for-10, switched his jersey number from 50 to 5. The latter, he said, "is more like an infielder's number." In fact, the list of Giants infielders who wore No. 5 includes Ray Durham, Juan Uribe and Ryan Theriot. Duffy added with amusement that left-hander Jeremy Affeldt told him the two-digit number 50 looked as if it wrapped around the rookie's slender torso.