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.