Welcome from the mountains of northeastern Oregon!
edinwa, you'd have to be more specific in your question. Because "laws" vary within any state, depending on what and where you're doing it. So, for example, do you mean state-owned parks? Because bear in mind that even if you did read something about state owned parks there in that state, then that only applies to ...... doh .... state owned parks. It would have no bearing on other types parks (city, county, federal, private, etc...). And bear in mind that not all state land is state "park" land. Not all federal land is federal "park" land. BLM is another example of a type of federal land. And road right-of-ways are an example of land that's not "park" land. And so forth. Rarely ever is there anything so specific on a city and county level, btw.
Anyhow, you need to be more specific and ask which type place and location you're asking about.
Or .... you can just take the stance of going any place it's not posted to the contrary. I mean, sure, use common sense and avoid tromping around obvious sacred historic monuments. But when it comes to typical schools, parks, beaches, forests ......... then ..... were you planning on wearing neon orange and going in the middle of an archie convention?
