I had heard that if was closed somewhere (probably in gossip with a neighbor??) , but in response to your question, I did some internet research and on the NH Dept Saftey, Bureau of Marine Patrol website,
http://www.nh.gov/safety/divisions/s...estricted.html
found the following:
"Pickerel Pond - Laconia
Boat/Motor Restriction - Seaplanes prohibited."
So if Laconia airport is not up to date, it seems to be behind the times.
I do not know when the change was made. I do not know if it is weeks or years since this decision was made. I had heard from someone it was illegal, and currently living there, was surprised to find a plane breaking the law.
The Bureau of Marine Patrol has a list of all bodies of water with a restriction of some sort, not all are seaplane restricted.