You require something the bot won't have that a human would.

Anybody may watch the demo screen of an arcade game for free, but you have to insert a quarter to play — and you can have even greater access with a key.

> and you’ve explicitly left a sign saying ‘you are not welcome here’

And the sign said "Long-haired freaky people Need not apply" So I tucked my hair up under my hat And I went in to ask him why He said, "You look like a fine upstandin' young man I think you'll do" So I took off my hat and said, "Imagine that Huh, me workin' for you"