[William Tell]

taxcontrol said: "I could postulate a number of potential offenses, ..."

Of course, you could.

But the criteria is that you must have evidence. What evidence, aside from carrying a rifle, would allow you to detain Grisham for poaching?

[taxcontrol]

You are incorrect. Evidence is NOT required, probable cause is NOT required. What is required is “reasonable suspicion” a much lower standard. See Terry vs Ohio