In regards to access to Maine areas, it does have a great ponds law that guarantees public access to water bodies over 10 acres even if that access is over private property. For some background see
http://en.wikipedia.org/wiki/Great_pond_(law)
http://www.mainelegislature.org/legis/Statutes/17/title17sec3860.html
Just because the legal right is there, doesnt mean that a landowner cant try to keep people off their land, its just that if it goes to court they have a shaky leg to stand on. The landowner does have the right to block their private roads with gates to prevent vehicular access so if the pond is 40 miles in on a logging road, its not particularly practical. Generally the right is for "fishing or fowling", so make sure you have your shotgun or fishing rod strapped to the boat
. A similiar law applies to the intertidal zone along the coast, folks have no inherent right to lay out on a beach towel on a private beach but they do have the right to fish or fowl.
Many towns along the coast had established "seashore drive" or some equivalent long ago to retain public access to intertidal zones, unfortunately I am not sure if all of them filled out the paperwork to retain these "paper streets" several years back when the rights would revert to the abutters if the towns did not reclaim their rights. Many of the islands off Portland had these. Prouts Neck a very exclusive colony n Scarborough Maine, used to have a "seashore drive", all the way around the neck on the seashore, if you tried to access from the adjacent state beach, a guard would meet you as you walked across the posted beach and hassle you. If you directly told him you were accessing the public right of way, he would grumble and let you pass, but if you didnt say the magic words, he would threaten you with arrest. (I dont know if Scarborough retained the rights so better check before you go) .
Is this access convenient, with a nice parking lot and boat ramp, not really but it is there, you just have to look for it and know your rights. I expect that was the intent of the NY case to make sure that a public right is not being infringed upon by a private landowner.