But the timing - four days after the voracious predator fish was found in a Montgomery County pond - angered legislators who thought the prohibition was imposed last year.
Frosh, a Montgomery County Democrat, sponsored a bill last year that gave the Department of Natural Resources authority to prohibit possession of the northern snakehead, a destructive Asian species that devours other fish and can live out of water for extended periods.
The legislation, enacted after snakeheads infested a Crofton pond in 2002 and spawned hundreds of juveniles, authorized DNR to adopt regulations prohibiting the "importation, possession or introduction into state waters" of invasive aquatic life.
Frosh said the measure was aimed specifically at ridding the state of snakeheads.
"I didn't realize they had failed to promulgate the regulations," he said.
A fisherman snagged a northern snakehead Monday in Pine Lake in Wheaton Regional Park, prompting officials to close the 5-acre pond and drain it.
The operation is expected to cost $10,000 and keep the lake closed to fishing for about three weeks.
Draining operations continued yesterday. No more snakeheads have been found.
Frosh said that even if the Department of Natural Resources had imposed a ban more expeditiously, it still might not have prevented someone from dumping the snakehead in Pine Lake. The fish caught there is estimated to be more than 3 years old.
"It could have predated any ban, and ended up in that pond anyway, I guess, since it's more than 3 years old," he said.
DNR officials say they never imposed a snakehead ban because federal regulations prohibit their importation, and state regulations make dumping them in waterways illegal.
Pet store owners also raised concerns about the effects of a ban, they say.
"There were some concerns by the pet store industry that the regulations would be more restrictive than they had to be," said Peter Jensen, DNR's deputy director.
Jensen said there was no agreement - among pet store owners and state officials - over what to prohibit.
"One issue was, do you just prohibit the northern snakehead, or the roughly 30 other species as well?" Jensen said.
"Where do you think DNR folks are going to go to look for snakeheads if there's a ban? The pet stores," said Ruth Hanessian, a Rockville pet store operator who works with businesspeople on state regulatory issues. "Leave us out of it."
Although Maryland pet stores do not sell northern snakeheads, a ban on them would confuse the public and prompt state inspectors to confiscate the wrong animals, she asserted.
A number of less-damaging snakehead species are available in pet stores - varieties that pose no threat to Maryland waterways because area water temperatures would kill them, Hanessian said. She added that the northern snakehead is unpopular because of its appearance.
"They're just ugly," she said.
Jensen said that the state's proposed ban on snakeheads will have to go through a series of public reviews before it is enacted.
He said the rules will be drafted in the next 30 days.
Like most state regulations, they must be published in the Maryland Register for a 90-day to 120-day review before they can become law. He said the review period ensures that anyone affected by the law has a chance to express his views.
But at least 20 other states have imposed a ban on the sale, ownership or release of snakeheads - largely as a result of the Crofton episode.
"After that incident [in Crofton], a number of states took steps to outlaw even its possession," said Ken Burton, a spokesman for the U.S. Fish and Wildlife Service in Washington.
Montgomery County officials are planning to enact emergency legislation that will prohibit possession of northern snakeheads.
The prohibition is expected to take effect next week.
County officials said yesterday that residents with snakeheads may turn them in to the Montgomery County Humane Society, 14645 Rothgeb Drive, Rockville. The phone number is 240-773-5960.