Baseball and smokeless or chewing tobacco have a long history together, but that association is about to come to an end - at least in San Francisco.

A ban on all forms of smokeless tobacco use at any of the city's sports venues, including the San Francisco Giants' AT&T Park, will go into effect next year on Jan. 1.

San Francisco Mayor Ed Lee signed the ban May 8 that will make it illegal for any person, including players, to use smokeless tobacco, including chewing tobacco and "moist inhalable snuff" at the venues.

Giants Manager Bruce Bochy said he supports the city's actions.

"It's a step in the right direction," he said on the Giants website. "I think it can be a good thing."

Bochy, whose has been an on-and-off user of tobacco over the years, added it would be a tough transition for some players. "It's going to be hard to enforce. It's a tough habit to break."

The Campaign for Tobacco-Free Kids, based in Washington, D.C., had worked to convince the city to enact the ban.

"Mayor Lee and the board of supervisors understand that athletes are role models for impressionable youth," campaign head Matthew L. Myers said.

"When baseball stars use smokeless tobacco, the kids who look up to them are much more likely to as well. Our national pastime should have nothing to do with promoting a deadly and addictive product," he said.

Giants star pitcher Madison Bumgarner, who like many players uses smokeless tobacco, said he would honor the wishes of San Francisco and try to abide by the ban - at least for home games.

"I quit every once in a while, for a while, just to make sure I could do it," said Bumgarner. "I guess I will (try quitting again) if they enforce a rule you can't do it."

Although smokeless tobacco use was banned at the minor league level more than 20 years ago, there has been no such league-wide ban in the majors.

The league tried to get the player's union to accept a ban in 2011 during that year's contract negotiations, an attempt that failed.

Asked about the San Francisco ordinance, MLB Players' Association spokesman Greg Bouris said, "We're aware of the signing of the law and have no public comment at this time."

There is legislation currently being considered by California Assembly that would prohibit both smoking and chewing tobacco at all major league stadiums in the state.