The plastic bag police scored a victory in Seattle this week. The liberal enclave imposed a ban on plastic bags and a 5-cent tax on paper bags, joining other major cities in the latest nanny-state crackdown sweeping the nation.

Seattle’s ban applies to all grocery, retail and convenience stores. It exempts farmers’ markets, however. The ordinance takes effect in July 2012.

Seattle’s action comes three years after the City Council tried to impose a 20-cent tax on all bags. That idea was shot down by voters in a referendum. It’s unclear if the new ban will also be challenged at the ballot box.

Environmentalists left little to chance before this week’s vote. Supporters dressed in plastic bag costumes and serenaded the City Council about the supposed dangers of the 100 percent recyclable plastic bags.

“Reducing the use of single-use plastics, like bags, will make a difference for the health of wildlife in Puget Sound and out in the Pacific,” said Heather Trim, policy director of People for Puget Sound.

But others questioned if Seattle’s new law would live up to the environmental benefits touted.

Marc Gunther, a senior writer for GreenBiz.com, argued that plastic bag bans aren’t based on science and suggested recycling could be a more attractive alternative. He also noted that bag waste might not be as bad as the anti-plastics lobby implies.

One of the largest U.S. plastic bag manufacturing and recycling companies certainly believes that’s the case. Mark Daniels, vice president of sustainability and environmental policy for Hilex Poly, told the New York Times that Seattle’s approach was “badly misguided.”

“Moving consumers away from plastic bags only pushes people to less environmentally friendly options such as paper bags, which require more energy to produce and transport, and reusable bags, which are not recyclable,” he said.

In addition to exempting farmers’ markets, plastic bags will be allowed at food banks, and for use with produce, bulk foods and meat, according to the Seattle Times. Restaurants can use plastic bags for takeout and low-income individuals won’t have to pay the 5-cent tax on paper bags.

Seattle, usually known for succumbing to eco-fads first, follows other municipalities like San Francisco, Washington, D.C., and Portland, Ore., which already have bans or taxes on bags.