I don't, in fact.

• I didn't make any assertions about them. A simple assertion that "the law has regarded" anything, without any reference to what law, is at least useless, and arguably worse. That was my principal point in that post.
• I also claimed not to know of any cases directly applicable to your example. (I know of no such cases; I am somewhat cognizant of a variety of cases that have gotten some publicity, but the ones I have heard of typically involved an AP operated by a commercial or government entity.)
• Oh, and I threw in a humorous jab at the DMCA, which seems to make more or less any activity involving a computer possibly illegal, at the relevant court's discretion, but is not directly related.

So what gave you the idea that I "understand the legal principles very well"?
I was just (snarkily) pointing out that your analogy, which you correctly said was legally different, was weaker than the sprinkler-water analogy initially proposed.

FWIW, you seem to be confusing things a little; either forbid the sheep, or forbid the neighbor from letting wireless communications onto your property; the latter may actually be within your rights, if his communications are causing interference.

Really though, I suspect* the difference has less to do with radio waves vs. sheep or forbiddability than with the two-way nature of the communication; you interrogate the neighbors router, eliciting responses it would not otherwise have produced. I expect** simply packet sniffing traffic without any transmission is not considered illegal in as many jurisdictions as actively connecting to an AP and downloading your own data.
*Disclaimer: suspect in this context is used merely to introduce a supposition which seems likely, and is not intended as and should not be interpreted or construed as a suggestion of competency, legal-principle-understanding, paralegal status, or bar licensure in any state, province, nation, region or planet.
**Disclaimer: expect in this context is used merely to introduce an inference, and is not intended as and should not be interpreted or construed as a suggestion of competency, legal-principle-understanding, paralegal status, or bar licensure in any state, province, nation, region or planet.