"2. The owners of the private property never objected to the protester's presence there. In order for being on someone else's property to be considered trespassing, the owner has to not want you to be there (e.g. if I walk through a church parking lot and nobody complains, that's not trespassing)."
The owner's have protested about OWS multiple times. The Police have simply stalled in their actions.
"3. The private property in question was actually required, by city ordinance, to be open to the public at all times, so even if they had objected they weren't allowed to do anything about it."
City Ordinance's also make it illegal to camp there. So they're clearly violating that.
Look, the reality is that if I or any other Joe Schmoe just showed up at a NY park, setup a tent, and said we're protesting _______________ and plan to stay until ____________ is achieved, the police would have you out within a few hours, at most. Far from being singled out for unfair treatment, OWS is getting especially kind treatment. The idea that they're peacefully protesting and therefore whatever they do is automagically legal is absurd and 99% of the people advocating that on slashdot would never want that made into law. Would you want peaceful anti-abortion zealots to be able to squat indefinitely in any clinic they don't approve of? Can I setup a camp in front of Old Faithful in Yellowstone because people don't respect The Bears properly? Can I and 100 friends setup camp in your house until the US government "does something" about Australian mistreatment of aboriginals?
Having a right to assemble doesn't magically make all other laws irrelevant, just like Freedom of the Press doesn't mean I can steal paper & ink to put out my newspaper. It certainly has never been interpreted that way in the past and even the people who support OWS today don't really want it to change the laws. They just want the laws changed for them only. Their attitude is, "I like OWS, so whatever they do is legal."