GRAND RAPIDS, Mich. - A big-game hunter who legally killed a polar bear more than a decade ago in Canada ran afoul of U.S. authorities after using a boat to ferry the trophy to Michigan.

Rodger DeVries, 73, of Ottawa County's Georgetown Township, faces sentencing Sept. 8 on a misdemeanour charge of knowingly and unlawfully using a U.S. port or harbour to import polar bear parts without obtaining a permit, the Grand Rapids Press reported.

Court records show he pleaded guilty Monday in U.S. District Court in Grand Rapids.The charge carries a maximum sentence of one year in jail and $100,000 in fines.

"The polar bear is an ecological and cultural treasure of the American and Canadian Arctic," Ignacia Moreno, assistant attorney general for the Justice Department's Environment and Natural Resources Division, said in a statement Wednesday. "We will not tolerate the illegal importation of polar bear trophies."

Defence lawyer Terry Tobias described DeVries as an "avid hunter" who has acknowledged his mistake in not getting proper U.S. permission.

He obtained proper permits from the Canadian government, including an export permit, and complied with Indian and province laws.

"Our laws don't prohibit going to Canada and shooting a polar bear. Where he made his mistake was, when he brought it back to the U.S.," Tobias said.

DeVries paid an outfitter $12,500 for the hunt, and the bear was killed in November 2000 in Nunavut and mounted by a taxidermist in Calgary. It was kept in storage until 2007, when authorities said DeVries moved the bear and its skull to Sault Ste. Marie, Ont.

In July 2007, DeVries, his son and two grandchildren drove in his truck, hauling a boat, and picked up the bear and skull, and the boat was used to cross the border from St. Joseph Island in Ontario to Raber Bay, north of St. Ignace, Mich., the newspaper reported.

His son drove the truck to the U.S. and picked up the others in the boat, according to a plea agreement signed by DeVries. The bear and its skull were taken to DeVries' second home on Torch Lake, and later were taken to his Georgetown Township home, records showed.

Since 2008, when polar bears were listed as "threatened" under the Endangered Species Act, the Marine Mammal Protection Act has prohibited the importation of polar bear parts or trophies for personal use from Canada, the Justice Department said.