Suppose you're a landowner in Germania, just west of the Rhine. It is the 2nd Century A.D. You own a number of farms, a couple of good houses, maybe some slaves, some of whom are on the verge of buying themselves out. You've just paid your taxes.
The publican whose duty it is to collect taxes in your area sends his agents to you demanding you pay again. Something has gone wrong somewhere, the publican's office is short of the expected budget. It's a shakedown, pure and simple.
You tell the agents they're mistaken. They tell you they don't care, and you'd better pay up right now. A dozen cutthroats show up armed to the teeth to back up the agents' claim. You've got no choice. You pay.
The following week, the agents show up again, accompanied by two dozen cutthroats this time, and simply tell you that you have to vacate the premises now: your land, with everything on it, belongs to the publican, effective immediately. You tell them the land has been in your family for three generations. They call you a liar.
You ask them to give you an hour. They agree. You take a bath, put on your best toga, and rush to the magistrate. You explain the situation to him. The magistrate says:
"Can you prove it?"
"Prove that a) they made you pay twice and b) that they're illegally expropriating your estate."
What kind of proof would you have to present? Documents? A plaque? Would you have to produce witnesses who could confirm that the land is rightfully yours? Would there be a record in the Quaestor's office over in Rome? Would you, as the owner, have a copy of that record? Signed by whom? If signatures were important, who'd be called upon to verify them, what kind of specialist?