I think it's more like walking onto your neighbor's private land when they don't have fences or a "keep-out" sign, but also don't have any obvious sign allowing

I think it's more like walking onto your neighbor's private land when they don't have fences or a "keep-out" sign, but also don't have any obvious sign allowing people in either. Still a crime, but not particularly severe or abhorrent; whether it merits serious punishment probably depends on particular details.