I'm a customs official. In my 'industry' It's common to joke that we're the second oldest profession. Is there any truth to this? What are the oldest references to customs that we've found?

by Thoughtthroughthough
mikedash

I'm sure that there will be many earlier references, and hopefully others can point you in the direction of some, but it might interest you to know that the presence or absence of customs posts on the borders of Poland in 1349-51 is one of the most crucial bits of evidence that allow us to address the vexed problem of whether the Polish kingdom escaped the Black Death.

A post looking into this problem was voted Best of 2017 and goes into this issue in some detail towards the very bottom of what is a long set of posts.

iorgfeflkd

One of the oldest reports of border logistics may be the various descriptions of the Umma-Lagash border conflict in the 2500s BC in Sumeria (modern Iraq). This eventually lead to a war which is described in the Stele of Vultures. The border between Umma and Lagash was marked with clay cones on which the border treaty was written in cuneiform. Some of the text of these treaties (e.g. the Treaty of Mesilim and the Stele of Vultures) contains rules regarding the border:

Enakalli, ruler of Umma, set the border to the land. He carried a canal from the great river to Guedin . He opened the field of Ningirsu on its border ... to the power of Umma. He ordered the royal field not to be seized. At the canal he inscribed a stele. He returned the stele of Mesilim to its place. He did not encroach on the plain of Mesilim. At the boundary-line of Ningirsu, as a protecting structure, he built the sanctuary of Enlil, the sanctuary of Ninkhursag

and

The ruler of Umma to Eanatum does swear: “By the life of Enlil, king of heaven and earth, the fields of Ningirsu I shall exploit as an interest-bearing loan. I shall operate the levees up to the spring, and forever and ever(?) over the boundary territory of Ningirsu I shall not cross. To its levees and irrigation ditches I shall not make changes. Its steles I shall not smash to bits. On a day when I may cross over it, the great casting-net of Enlil, king of heaven and earth, by which I have sworn, upon Umma may it fall from the sky!”

(Source: Kramer, Samuel Noah. The Sumerians: Their history, culture, and character. University of Chicago Press, 1963.)