Karen Dittmer was arrested under the Social Host Law, which was enacted July 17, Nassau County police said.
Dittmer, 45, is accused of allowing her teenage son and several other underage guests to drink beer Sunday evening at a party for her birthday held in the backyard of her West Hempstead home.
She called her arrest "ridiculous."
I would never ever serve alcohol to a minor," she said. "I have three children of my own. I would never ever do that."
The new law, which was passed unanimously by the county Legislature, allows for homeowners or renters over the age of 17 to be held criminally responsible if minors drink in their homes.
First and second offenses will earn culprits fines of $250 or $500. On a third strike, offenders can face up to a year in prison and a $1,000 fine.
The law makes exceptions for alcohol consumed for religious ceremonies.
Similar measures were already in place in the local communities of Long Beach, Glen Cove and Amityville and around the nation in Virginia, Nebraska and parts of California.