This is a question about a place I have been going to since I was 16 (54 now). When I was younger I used to go a lot, camping there in both the winter and summer, swimming in the creek, and later taking my kids there (now grown). It is off the beaten path, there is vehicular access through private property.
This is in the mountains about 60 miles east of Pittsburgh, very steep valley (20 foot contours). 
The west side of the stream is state game lands. The road shown in purple does not actually cross the stream, that is a mistake on the USGS quad. The east side is private, owned by a lumber company. Never had any issues with them, like I said I have been going there 38 years.
The PA Game Commission recently posted their boundary. In addition, they posted signs saying swimming is prohibited in all lakes, ponds, creeks, etc on state game lands. The boundary between game lands and the private owner is the center of the creek. Here is what the creek looked like yesterday:
Here is a waterfall just below that, we would slide down the waterfall and also jump off of the protruding rock at the top. Note the yellow sign on the tree above the waterfall.

The rock is on the state game lands side, the boundary would I guess go down the middle of the waterfall.
My question is would they be able to enforce the no swimming prohibition? What if a person were to swim on the private side? People camp there a lot on the private side.
I have no idea why they posted it as no swimming after all these years, it has been state game lands since the 1930's, I believe.
My first reaction is to say that we need the public lands to be under new management.
Nate
Yea, here in PA you can't do ANYTHING (hardly) on SGL, except hunt. And, the game commission agents have gestapo like powers to stop and search your vehicle for illegal game, even off of their lands. They actually have more search powers than state police (from what I hear). And they own a LOT of land-1.4 million acres
They'll try to enforce it then it's the state against an individual. Who do you think has deeper pockets? And if you try to use a bar of soap to wash down they'll tie it to pollution. And God help you if it's in the Chesapeake Bay water shed.
> I have no idea why they posted it as no swimming after all these years, it has been state game lands since the 1930's, I believe.
PA Code
TITLE 58
PART III. Game Commission
Chapter 135. Lands and Buildings
§ 135.2. Unlawful actions.
(4) Swim in a dam, pond, lake or stream
My guess is they recently posted it because they discovered a reproducing population of Brook Trout
I have seen brook trout in that stream. That makes sense. I couldn't think of any reason why they would care, but that does make sense. The access to that area from SGL is impossible. It drains to the Youghiogheny about 1 mile downstream.
[sarcasm]You should be ashamed of yourself for enjoying that for the last 38 years.[/sarcasm]
That is probably what the signs mean. I know what I would do, likely end up with tickets and eventually jail time.
:good:
Bathing is typically a right associated with the Public Trust Doctrine which speaks to lands which are owned by states in their sovereign capacity, meaning, held in trust for use by the public.
I wonder how they get around that to interpret that they may prohibit bathing (swimming) in these public waters. Many of the colonial states have some significant differences in the way they interpret matters associated with both navagability and with sovereign ownership.
With this particular creek, it's pretty certain, based on the photos that it would not be navigable for title purposes (or any other purpose except possibly for some USACE or other environmental regulatory purpose). So whether or not there are Public Trust rights associated with it may depend upon whether the title history shows it to have been in continuous State ownership since Independence and to have been in continuous Crown ownership prior to that, or if it was acquired from a non-federal, non-state, non-Crown party at some point.
Is there a statute cited on the signs? If so, what exactly does the statute say?
YES
In PA, there are two types of navigable streams: navigable by fact and navigable by law. Very few are actually navigable by fact (generally the Delaware, Susquehanna, Allegheny, Ohio, and Monongahela and some of their tributaries). But there is a long list of streams that are navigable by law. This is not one.
There was an interesting case in court a few years back. A high quality trout stream (which was navigable by law) passed through the grounds of a fishing club that charged big bucks to belong, and they tried to restrict access to the portion of the stream that flowed through their property. They owned both sides. But, by law the commonwealth owned to the low water mark, and the private owner owned to the high water mark. Between the high water and low water marks there is a grey area where both the private owner and the commonwealth have rights.

The fishing club lost, and the public can walk through along the stream. Sort of defeats the purpose of the fishing club.
> Many of the colonial states have some significant differences in the way they interpret matters associated with both navagability and with sovereign ownership.
Pretty good summary in Shively v. Bowlby - 152 U.S. 1 (1894)
By the law of England, Scotland, and Ireland, the owners of the banks prima facie own the beds of all fresh water rivers above the ebb and flow of the tide, even if actually navigable, to the thread of the stream, usque and filum aquae. Lord Hale, in Hargrave's Law Tracts 5; Bickett v. Morris, L.R. 1 H.L.Sc. 47; Murphy v. Ryan, Ir.R. 2 C.L. 143; Orr Ewing v. Colquhoun, 2 App.Cas. 839.
The rule of the common law on this point appears to have been followed in all the original states -- except in Pennsylvania, Virginia, and North Carolina, and except as to great rivers, such as the Hudson, the Mohawk, and the St. Lawrence in New York -- as well as in Ohio, Illinois, Michigan and Wisconsin. But it has been wholly rejected as to rivers navigable in fact in Pennsylvania, Virginia, and North Carolina, and in most of the new states. For a full collection and careful analysis of the cases, see Gould on Waters, 2d ed., §§ 56-78.
The earliest judicial statement of the now prevailing doctrine in this country as to the title in the soil of rivers really navigable, although above the ebb and flow of the tide, is to be found in a case involving the claim of a riparian proprietor to an exclusive fishery in the Susquehanna River, in which
Chief Justice Tilghman, in 1807, after observing that the rule of the common law upon the subject had not been adopted in Pennsylvania, said:
"The common law principle is in fact that the owners of the banks have no right to the water of navigable rivers. Now, the Susquehanna is a navigable river, and therefore the owners of its banks have no such right. It is said, however, that some of the cases assert that by navigable rivers are meant rivers in which there is no flow or reflow of the tide. This definition may be very proper in England, where there is no river of considerable importance as to navigation which has not a flow of the tide, but it would be highly unreasonable when applied to our large rivers, such as the Ohio, Allegheny, Delaware, Schuylkill, or Susquehanna and its branches."
Carson v. Blazer, 2 Binney 475, 477-478.
:good:
Turning it around
OK, so what if I was the private adjoiner? And I said yes, you can swim in the stream. I think I have as much right to say that as they do to say you can't swim there, since we both own to the center (hypothetical, I don't own it).
Interesting, because in state parks and state forests you can swim in the streams, but not state game land. Their justification for being so restrictive in the game lands is that they say the land was purchased using money from hunting license fees, so it should solely be for hunting. No camping, etc.
I went on a nice hike in Ohiopyle state park Sunday, on a trail I had never been on. Here is where it took me after about a 1.5 mile hike:

Yes, you can swim there.
Turning it around
>I went on a nice hike in Ohiopyle state park
I used to spend a lot of my free time fishing the Yough back when I had free time.
:good: :good: :good:
That "gray area" you mention, and the portion that the court opinion said is subject to "the police powers of the state" is the same as CA and several other states refer to as the Public Trust Easement meaning that historically, common law has recognized the rights of the public in navigable waterways up to the ordinary high water mark, but since states may decide to assert sovereign ownership to the OHWM, the LWM, or none at all, the rights of the public (and regulatory or "police" powers of the state) exist like an easement from the OHWM down to the line of state sovereign ownership, or over the entire width of the navigable stream if the state is one that does not assert sovereign ownership of the bads of navigable waterways.
This particular case is different in that the state holds title to the center of a non-navigable waterway. So it becomes a three-pronged question: 1) what is the title history of the state ownership of that land? 2) What body of statute and/or regulation does the no swimming rule exist in? and 3) How have the PA courts weighed in (if they have at all) on the public's rights to non-navigable waterways that cross, are within, or form a boundary of state public lands.
Is the no swimming thing in the statutes or in the administrative code pertaining to DFG? If it's in statute and the State Constitution is silent on the matter, then there's not much to be done except to reminisce about the good old days before that law or before they applied it to this stream. If it's in the admin code, then it is a regulation promulgated by the agency (DFG) rather than a law passed by the elected legislature.
Anything that appears in admin code (agency created regulations) must have an authorizing statute behind it. Most, if not all states have a statutory body of administrative law that provides the framework within which administrative code is to be written, evaluated for consistency with authorizing statutes, public input, etc., so it's not common for regulations to get as far as being codified (published as part of the code) and enforced without statutory authorization. But it does happen from time to time as some agencies adopt regulations according to a very broad interpretation of their statutory authority on various matters.
Many state courts have now ruled on the public's rights to navigable waters in cases very similar to the one your post refers to wherein they differentiate between waterways which are navigable for purposes of sovereign title as opposed to those which are navigable in fact for small craft. Some states have also used a log floating test. Often, those courts reach the same conclusion that the PA court did in that the public has particular use rights (and the state certain regulatory rights) over such waterways even if there is no sovereign ownership in the underlying bed. These rulings may speak to the portion between a state's limit of asserted title (often the LWM) and the OHWM on an otherwise navigable (for title purposes) waterway, or they may address waterways which have no portion which are navigable for title purposes but are navigable for recreational and sometimes certain limited commercial purposes.
I'm not aware of cases which speak to publicly owned waterways which have no aspect of navigability, but they may exist in some states.
Thanks for that detailed response, Evan. I think it is interesting. Unfortunately I don't know anyone in the Game Commission, although I believe they do have surveyors on staff.
I had always wanted to buy a portion of the adjoiner, which is 1124 acres. I only wanted a measly 5 or 10 acres. Now I am getting to be too old.
Interesting history about the private parcel shown on the quad map on the west side of the creek, the one with three straight sides and the fourth side being the northerly portion of the creek. I had also always been interested in that parcel, but not as much. Deed says 200 acres, but I know it is much less. The long time owners were listed as living in Florida, I assume they were elderly and retired there. So I always kept my eye on that as well. Last time I went to that particular county courthouse a couple of years ago I saw that somone bouhgt that parcel for $40K and then sold it shortly thereafter to the game commission for something like $80K. Nice profit on that deal. So now the state owns all the land on the west side down to the Yough River, which is "navigable" (great white water rafting). But, there is still a religious camp at the bottom of the hill, on the left bank (west side) of the creek, riverward of the former Western Maryland RR (now part of the Great Allegheny Passage trail from Pittsburgh to DC. Not sure how that works, because that camp is fairly close to the river (i.e. inside the HWL).