Southampton Town police have arrested a former president of the Sag Harbor School Board on a misdemeanor charge of allowing teens to drink alcohol at her North Haven house. Police arrested Susan E. Guinchard Kinsella, 54, at home on Friday, alleging she violated Suffolk County’s Social Host Law. The law prohibits any adult who “controls a private residence to knowingly allow the consumption of alcohol or alcoholic beverages by any minor.” She was released with an appearance ticket. Claiming that she never should have been arrested, her attorney, Daniel G. Rodgers of Southampton, said Sunday that the word “knowingly” in the law was key. “To establish or suggest a violation of the Social Host Law,” he said, “they have to prove that the defendant had knowledge” that alcohol was being consumed. “This came as a complete shock to her.”Ms. Guinchard Kinsella was arrested after a three-week investigation into a party reportedly held by her daughter at their Barclay Drive residence on Jan. 27. According to police, they could see young people inside the house consuming beverages when they arrived that night, but Ms. Guinchard Kinsella would not allow them to enter.Police had gone to the house as a result of an anonymous call. They reported that after being barred from entering, they stayed in the area and interviewed teens as they left the house. The arrest occurred after a follow-up investigation. “This is a woman who cares deeply about young people,” Mr. Rodgers said. “Her service to her community ends up being a negative, rather than a plus,” he said, wondering aloud whether her status influenced the charge.Besides being a past president of the Sag Harbor School Board, Ms. Guinchard Kinsella previously headed the school district’s PTA. She is due to be arraigned in Southampton Town Justice Court on March 10.Barclay Drive is in a gated community known as West Banks. The call about the alleged party came in to state police on an anonymous tip line, 866-UNDER21, set up to encourage reporting of events at which minors are thought to be consuming drugs or alcohol.The incident occurred two days before a party at a Neck Path house in Springs at which an 18-year-old former East Hampton High School student, Jordan Johnson, overdosed. He survived but was seriously paralyzed and was undergoing rehabilitation in Manhattan. An article on that case appears elsewhere on this page.