Whether the off-field landing site is approved by others may be the crux of why this enforcement action took place. As a matter of regulatory procedure, you're correct: there's no regulation which stipulates a specific approval of an off-field landing site.
Consider the choices, and it's not a matter of Alaska as a free-for-all, and the remainder of the planet being tenuous and a risk. Land 500 miles from anywhere on a flat piece of land where no one sees, no one knows, and which has no environmental impacts, no significant political, historical, or other importance, no cameras, and one will pass through history as invisible. Legal? Sure.
Now put a crowd of boy scouts having a jamboree there. Land a mile from them. Not really a problem. Move the landing closer, still unlikely a problem. Now land between their tents. Problem. Where does it become careless and reckless? Where does it begin to violate proximity and regulatory standards? This becomes a sliding scale answered by several questions and also applicable to the specific case: what's a problem for one landing is not for another.
If no one reports the event, records the event, it may pass unnoticed. If the event is captured on cell phone videos, observed by FAA inspectors, put online by the pilot or the scouts, then the possibility of enforcement action increases. An inspector who feels a regulatory violation has taken place may initiate enforcement action, which then moves up the ladder from the FSDO to the regional office and becomes a legal question, in this case addressed with appeals and counter arguments before an Administrative Law Judge. This isn't a one-off snap-action by an overzealous inspector, and has been examined and reviewed by numerous persons, including a judge.
Can I land in a crowded walmart parking lot? Maybe; in an emergency many regulations are waived, so an engine-out situation with a forced landing might necessitate a small corner of the lot as my only choice. Can I land on a city street? That depends on the street, and the circumstances. A rural road? Again, it depends. A flat piece of highway miles from any obstacle or any person? Most likely not a problem, but specifics matter. Adjacent to various homes? Depends. Runway nearby? Purpose for landing? We dont get to call any point a landing point and thus excuse ourselves from the regulations. Otherwise we could drop into that crowded walmart parking lot on a whim. Simply stating that any place we choose is acceptable and a landing point, is a convenient excuse..."except when necessary for takeoff or landing"...but that isn't going to hold water if there is no valid reason to be landing at that site, or if the site is deemed unacceptable.
In the case of the talking head on the video, his own admission is that he couldn't land because he couldn't identify not only a place to touch down, but the centerline of the "runway," He couldn't identify it as a landing site and went around and chose not to land, ultimately. Who rejected it as a landing site? He did, and he flew elsewhere. He told this to the FAA, to the ALJ, and posted it online and on videos to broadcast his choice. He met with the FAA without counsel and told the inspectors about this.
"Except when necessary for takeoff or landing" is a valid reason, spelled out by regulation, by unspoken is the reason for the takeoff or landing, and it does matter. We can be excused from adherence to any rule or regulation when we take actions necessary to meet the demands of an emergency; this policy is at the core of what we do. Unspoken in this permissive core, however, is whether the emergency was one of our own making. Our engine fails, and we put the airplane down in that Walmart parking lot. No one is hurt, and we've saved the day. But the airplane ran out of fuel, because we failed to plan properly; we created the emergency. Now we're idiots who got lucky. Or we shut off the fuel to make a simulation more realistic for a student, and the fuel selector failed in the off position. We've caused the emergency. It's no longer an excuse for landing in that Walmart parking lot. The emergency is real enough; and we can bypass the regulations necessary to meet the demands of that emergency...so on it's face landing in that Walmart parking lot is a response to an engine-failure...but there's more to the story. That careless and reckless operation (91.13) aspect will revolve around the reason for the emergency.
Be careful of scars earned in battles in which we should never have fought, and of emergencies that we create. It's one thing to respond to the need of an emergency, but entirely another if we create the emergency.
Likewise, not all landings are necessary. A landing in the Walmart parking lot to deal with an emergency is generally a no-brainer (though would certainly be tempered in argument, as to whether other sites were available or better choices as well as the outcome of the landing, injuries, property damage, etc: the totality of the event will be considered). It's a no-brainer because of an emergency. Take away the emergency element, and the Walmart parking lot becomes a lot harder to justify as a landing site. It it isn't justifiable as a landing site (landing there isn't necessary), then it invalidates the argument that proximity to persons or objects is justified by takeoff or landing. Such relief from the regulation is not justified by an illigitimate landing site, any more than relief from the regulation is justified by an emergency we create, or by the perception of an emergency, which is not.
The subject pilot doesn't claim emergency authority here (which I cite for the purpose of illustration), but rather that his proximity to persons or objects was necessitated for the purpose of takeoff or landing. Whether the landing was necessary or not becomes an issue; not all landing sites are necessary, or viable. Therefore, we cannot claim any point on the ground is a legitimate landing site.
In the case of the rc airplane field at which the subject pilot attempted his landing, the pilot himself stated that the location wasn't viable. He rejected the choice and flew elsewhere.
We can't justify low altitude flight (in proximity to persons or property) as excepted from the regulation on the basis of necessary for takeoff or landing, anywhere on earth simply by stating that we intended to land at that point. Otherwise, we could buzz Walmart parking lots all day long, using that as our justification. It won't work. Not all points on the planet are justifiable landing sites. In this specific case, the pilot himself provides the most compelling case against his decision: he determined that it wasn't a viable landing site. The FAA doesn't need to reject it as a landing site. The ALJ doesn't need to make that decision, because the pilot did, and he made legal statements to the FAA in person (prior to retaining an attorney), and continued to make them, and now makes them with videos, and he argued it in front of a judge. The pilot states that the site wasn't acceptable; if it's not acceptable, then it invalidates using it as an excuse for low flight in proximity to persons or property.
He can argue grainy videos of videos as technicalities or semantics, but the admissions are his own, in person and on video, and he's taken time to broadcast it to the world.
I've spend most of my teen and adult life landing off field and flying low as an instructor and as a working pilot flying ag, fighting fires, and doing other such things. I've landed on mountainsides, fields, roads, water, and so forth, and flown under powerlines, bridges, between buidings, below rooftop level, and everywhere else one might imagine, in urban areas (even Disneyworld), and near structures, houses, people, cars, etc. I've routinely flown at low altitudes in close proximity to persons, often within a few feet, and have done it thousands of times in the course of my work. I understand the implications, the legality, and even the justifications (and necessities), and I'm very familiar with off-field landings, landing sites, and the choices and necessities involved. I get it.
I also understand the other side of the fence, and a private pilot talking head who made more than a few questionable choices, doesn't alter that fact, regardless of whether AOPA (et al) likes him. Among those questionable choices was his arrogance is talking to the FAA without representation or consultation (maybe he should have called AOPA legal, first), along with broadcasting himself online. That landing 500 miles from anywhere, with no one to see, has a greater chance of success because no one knows. Film it, put it online, and everyone knows. Make one's self a target, and someone might shoot at the target. Just give them a reason...like complaining neighbors, cameras, and one's own in-person and online confessions. As stated previously, it's very possible that no one could put this pilot in the airplane at the time of the alleged event...could have been anyone in that cockpit. In most cases of enforcement action, it's the pilot who puts himself in that cockpit by own words, written or spoken. The pilot who just can't keep his trap shut is his own worst enemy when it comes to enforcement action, and this guy (Trent) goes a step further; he can't keep his face off youtube. Look-at-me has it's drawbacks.
Who is watching, who is listening, and how much we say, has a great deal to do with the outcome. The event doesn't end when the propeller comes to a rest...what took moments to occur in real time may take months or years to settle in enforcement action, appeals, and judgements. Two years on, here we are; the talking head who couldn't keep his pie hole shut in the first place, still can't, and sympathy to his one-sided cause or "likes" by AOPA doesn't change the fact.