>You can't define some arbitrarily complex behavior that makes you into a trespasser. Maybe I'm wrong on that?

I've seen plenty of trespassing signs with statements mentioning specific times of day, like "after sunset" or "after midnight until 8am". I assume these are legally binding but I don't know for sure.

IANAL, but I think it comes down to the trespasser being informed in some way that the property is private and they're not welcome. If I'm kicked out of a store, for example, the owner or one of their agents has informed me that I'm no longer welcome on that property, so trespass happens if I try to come back. In the case of someone's property that has conspicuous no trespassing signs, the sign serves to inform me I'm not welcome.

At least that's what the cops told me one time when I was a kid and got busted exploring in the woods and missed the property owner's "POSTED" signs...

This is the commonly excepted folk advice people are given, however, most state laws (US) take no account of so called posted signs. There is a ‘mens rea’ requirement that for trespassing would typically require only that the trespasser knew they were on land that did not belong to them (this issue is easier to muddy if the trespassing occurs on ‘public’ lands/property).

But the statutory basis for trespassing is most often just the act of crossing into land without prior express permission.

I wanted to make sure I wasn't talking out of my ass about the posted signs, so I looked up the regulations for where I was from (New York): https://www.dec.ny.gov/regulations/2442.html#posted

But to be clear about my anecdote, I wasn't doing anything wrong and wasn't actually arrested. My family's property bordered the property I "trespassed" on, and the guy called the cops on me, a 10 year old, instead of just telling me to leave. The cop showed up and basically just scared me and said he didn't want to come back out there.

That would depend on the jurisdiction. Typically in the US, most states define two separate criminal statutes for each situation:

1) Criminal Tresspassing - typically defined as the entering the property of another without express permission from the owner (this tends to include intruding via drone these days)

2) Remaining or Reentry after forbidden - which is for those cases where entry was permitted, but the owner subsequently revoked that permission.

>this tends to include intruding via drone these days

Can you elaborate on this point? There are a LOT of FAA rules and federal laws that allow aircraft to fly over your property without your permission. I could see the argument for a ground-based device or perhaps an extremely low-flying drone but not for general drone use.

Of course, there are other laws (like requiring line of sight, not flying over humans or livestock, etc.) that are probably broken by anyone flying a typical non-commercial light drone over someone else's property at a level low enough to be annoying.

I happen to have this handy from a Motion:

Laws traditionally related to state and local police power – including land use, zoning, privacy, trespass, and law enforcement operations – generally are not subject to federal regulation. Skysign International, Inc. v. City and County of Honolulu, 276 F.3d 1109, 1115 (9th Cir. 2002). State and Local Regulation of Unmanned Aircraft Systems (UAS) Fact Sheet Federal Aviation Administration Office of the Chief Counsel, 2015.

> 1) Criminal Tresspassing - typically defined as the entering the property of another without express permission from the owner (this tends to include intruding via drone these days)

You generally need to be aware of it though, right? Wandering in the woods won't get you in violation if you accidentally cross property boundaries, there needs to be a fence or at least a sign informing anyone about the blanket "No Trespassing"?

Awareness is not really necessary. Even in the absence of a fence and "No Trespassing" sign, they can still get you for criminal trespass. If, for instance, you go onto old lady Johnson's lawn and help yourself to all of the spinach in her garden or the roses in her rosebush. (Well, assuming she wants to press charges that is.) She doesn't have to have a fence or "No Trespassing" sign.

That's theft or destruction of property.

That's why they'd charge you with misdemeanor theft and criminal trespass. (Unless for some reason old lady Johnson's flowers and veggies were extraordinarily valuable on the open market.) If old lady Johnson is the prosecutor's grandma, you'll also likely see a disorderly conduct charge. And you'd better hope you don't live in a jurisdiction with robust menacing statutes.

Point is, any prosecutor can start stacking these charges and land you in a world of hurt for whatever reasons they please.

I remember vividly a night in college when I got a ticket for underage drinking at a house party. I was wishing I had gone with my friends to a bar downtown. Until they got back later that night and I found out that a bunch of them got cited for underage drinking, disorderly conduct, and also got forgery charges. (Because of the fake id's they used to enter the bar.) In essence, they had done the exact same thing I did, only difference being the cops that busted the house party didn't search everyone and find fake id's on us. All those other charges were totally unnecessary, but they got stacked on anyway because the prosecutor and/or cops wanted to be hard asses.