WINNIPEG (CP) - As the northern Manitoba town of Leaf Rapids prepares to become Canada's first plastic-shopping-bag-free zone, some lawyers and plastics industry advocates are questioning whether the ban could withstand a legal challenge.

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When the municipal bylaw comes into effect Monday, retailers will no longer be allowed to give away or sell plastic bags intended for single use. Scofflaws will face penalties of up to $1,000 a day.

Town administrator Bond Ryan says the law will help the environment by keeping the bags out of the landfill, save the town money in cleanup costs and protect the town's image as an international fishing destination.

"This is just one small thing that's going to go a long way," said Ryan, who spearheaded the bylaw.

Ryan said the town did not consult with a lawyer before drafting the two-page bylaw, but he's confident it falls within the town's jurisdiction under the Manitoba Municipal Act.

"Towns have the right to ban stuff that defaces their town, and to help make their town look good."

Meanwhile, San Francisco became the first U.S. city to outlaw plastic bags, signing off on a new plan late Tuesday that requires supermarkets and pharmacies in that city to switch over to environmentally friendly compostable bags made of corn starch or of recycled paper.

Environmentalists say 180 million plastic bags are distributed in San Francisco each year.