I disagree. Here is the text of the most current code I could find (Decide 2018):
(2) Entering or remaining upon or in property without justification after being notified or requested to abstain from entering or to remove or vacate there from by the owner, lessee, or person in lawful possession, or the agent or employee of the owner, lessee, or person in lawful possession, or by any peace officer, magistrate, or public employee whose duty it is to supervise the use or maintenance of the property. A person has been notified to abstain from entering or remaining upon or in property within the meaning of this subparagraph (2) if any of the following is applicable:
(a) The person has been notified to abstain from entering or remaining upon or in property personally, either orally or in writing, including by a valid court order under chapter 236.
(b) A printed or written notice forbidding such entry has been conspicuously posted or exhibited at the main entrance to the property or the forbidden part of the property.
Now, I would never do it, but this seems clear I can enter ANY private property that I have not been told to stay out of and it can't be prosecuted as tresspassing. That notification can be in person or via sign (or purple paint if this passed).
I agree that law needs changed, but until it is, I will support cheaper and easier ways to provide notification.