CHICAGO -- Even as a 10-year campaign to block wholesale export of Great Lakes water came to a successful conclusion in Congress last week, some legislators and environmentalists vowed to continue their fight to close a "bottled-water loophole," a campaign that taps into a national debate over sales of H2O in disposable containers.

A provision of the Great Lakes Compact allows water to be diverted from the basin if it is in containers holding less than 5.7 gallons. The question is whether bottling water from the aquifers that feed the lakes, the largest repository of fresh water on Earth, should be seen as ordinary human consumption, commercial production, or export of a treasured natural resource.

In August, Nestle Waters North America was granted permits for a new well and pipeline at its Ice Mountain facility in Mecosta County, Mich., where it bottles 700,000 gallons a day. Nestle also recently renewed permits for its plant in Guelph, Ontario. Both have sparked vocal opposition from those who say the industry is privatizing a public good and harming the environment.

Americans drank 8.8 billion gallons of bottled water in 2007, up 7 percent from 2006, according to the Beverage Marketing Corp. But bottled water has drawn increasing criticism, leading San Francisco, Salt Lake City and Ann Arbor, Mich., among other municipalities, to ban buying bottled water with city funds.

Nestle spokesman Brian Flaherty said the industry is being unfairly singled out, since it is only one of many commercial sectors that use and export water. More Great Lakes region water goes into soda and beer cans, he said.

"How do you define a product?" he asked. "Water goes into beer in Wisconsin and radiators in Detroit. Why would you have a separate standard for bottled water versus soda?"

Bottled water accounts for less than 0.02 percent of groundwater withdrawals nationally, according to a 2004 University of Maryland study cited by the International Bottled Water Association. Fourteen times as much bottled water is imported into the Great Lakes basin than is exported, a U.S.-Canadian commission reported in 2000.

But opponents of bottled water say soda and beer are different because the water is consumed in making something else, whereas they view Nestle as taking a public good, paying very little for it, and making a profit on it.

They also fear that since the compact officially treats water as a "product," the door could be opened to further commercialization and sale. It was such fears that in 1998 launched the process that led to the compact, after the tiny company Nova Group obtained a permit from the Ontario government -- later withdrawn -- to ship up to 158 million gallons of Great Lakes water per year to Asia.

Rep. Bart Stupak (D-Mich.), who led opposition to the compact because of the bottled-water loophole, has requested comments from the Office of the U.S. Trade Representative and the State Department about how international trade issues will play out.

"Call me all wet, but I say, why don't we get the answers? Why are we rushing this?" he said.

Anu Bradford, a University of Chicago law professor, said international trade law cannot force a country to extract its natural resources -- such as water "in its pristine form in a lake." But once it is bottled and becomes itself a product, she said, trade agreements would prevent a ban on exports.