Even if we considered the nature of the beam itself (as argued in the briefing), rather than its effect on the appearance of the property (as argued orally), I am not sure the district court injunction could stand.

The Respondents argue that the beam of light itself is, by definition, a “tangible” thing that can “invade” real property. This argument derives from the language commonly used by various courts attempting to define the tort of trespass. According to the Respondents, light is a physical thing that can invade and therefore trespass onto property; according to the Union, it is not. Tracking the traditional judicial language, my colleagues conclude that the light projection at issue here did not constitute a tangible property invasion, and I agree.

But what does it really mean to say that something is “tangible” or amounted to a “physical” invasion? The Respondents do not allege that their property was physically harmed or damaged in any way; that their access to the property was impeded or obstructed by the Union’s activities; or that the Union attempted to possess or appropriate any portion of the property in any way, at least in the traditional sense of physically occupying space that belonged exclusively to the Respondents by virtue of their ownership of the land under the law of real property.

Rather, the argument made here is that the light projection constituted a trespass because light is composed of “particles” (according to the Encyclopedia Britannica, which the Respondents cite in their brief), and those particles are tangible and therefore capable of physically intruding across the Respondents’ property line. But whether something is “tangible” or not does not seem to me to be a proper or clear legal test, at least not one that can be readily understood and applied to a wide range of facts.

Instead, the argument strikes me as a syllogism based upon superficial pseudo-science, and I am not sure that the outcome of this case ought to be governed by this kind of approach.

As an initial observation, the science relied upon by the Respondents appears to be wrong, or at least incomplete. If one really wants to get into the physics of the question, light has the properties of both a wave and a particle. Scientifically speaking, light sometimes has the qualities of a particle and sometimes has the qualities of a wave, and, to make things even more complicated, it can have both qualities at the same time. So the scientific answer to whether light is a particle or a wave is that it is both; therefore, following the Respondents’ syllogism, sometimes light is arguably physical and sometimes it is clearly not. If this is our inquiry, then we are dealing with nothing more than an exercise in subjectivity, something akin to a Rorschach ink blot in which any judge can find a trespass, or not, depending on his or her personal predilections because both conclusions would be supported by the underlying science of the matter. But as a method of legal analysis, that gets us nowhere fast.

More fundamentally, technical merit aside, scientific analysis and legal analysis are two different modes of inquiry designed to accomplish very different goals. In science, data-based objective truth is all that matters. In law, courts care about the “truth” in the sense of achieving a just (or “right”) result in a particular case; but they also care about other things and can sometimes sacrifice individual truth in order to achieve other important policy goals, such as making the law predictable, consistent, stable, and clear even if not well-matched to the facts of every individual case.

Consequently, even if it were unequivocally true that a quantum physicist would think of light as formed of particles, that conclusion alone should not govern whether we should find a trespass here as a matter of legal analysis and underlying public policy. There is a place for science in drafting and interpreting the rules that govern human conduct, but determining what scientists may think about a matter in legal dispute is not the ultimate goal of what courts do.

Properly framed, I think the question before us is not whether light is tangible or not, but instead: what legal right inherent in property ownership does the light projection supposedly violate? …

Fundamentally, the right to own property is the right to exclude others from entering, using, or possessing it. In a real sense, whenever property is bought or sold, what has really been purchased is the right to sue someone in court for trespass for entering, using, or possessing the property without the owner’s permission.

The Nevada Supreme Court has said that a trespass occurs when a property right has been physically invaded. Alternatively, the tort has also been described more broadly as protecting against “[a]ny misuse of the land or deviation from the intended use of the land.”

But these are relatively generic phrases, and it is not entirely clear how they can be applied to the particular facts at hand…. Fundamentally, the problem here is that we are confronted with a clash between very old law and evolving new technology. Trespass is one of the oldest torts known to Anglo-American jurisprudence, dating as far back as twelfth-century England. But back then, even the most advanced thinkers of the day were not aware of such things as atoms, electrons, or photons ….; it would be another two centuries before Galileo proved that the earth revolved around the sun, a revelation so antithetical to prevailing thought that he was burned at the stake for suggesting it.

It should come as no surprise, therefore, that the tort of trespass was originally limited to physical invasions of property by people or objects composed entirely of matter; as far as anyone knew, there was nothing else that existed in the universe that could invade anything. In an era lit by wax candles, and then whale-oil lamps, and then kerosene, there was not much that one could do to another’s property with light.

But nowadays light can be so many more things and can be used in so many more ways; searchlights, lasers, and light projectors of the kind involved in this case are now commonplace. The inquiry here is whether the bundle of rights traditionally protected by the ancient tort of trespass should be read to include the right to stop the newly-developed light projection used here.