Adjacent to them worked Melatiah the Gibeonite and Jadon the Meronothite, who were men of Gibeon and Mizpah. These towns were under the jurisdiction of the governor of Trans-Euphrates. (NET Bible)
The NET Bible translation note tells us that “under the jurisdiction” is literally “to the seat” in the Hebrew. The wording of the last part of the verse, including ‘Mizpah’, is ‘וְהַמִּצְפָּה לְכִסֵּא פַּחַת עֵבֶר הַנָּהָר’. It is usually interpreted somewhat abstractly, as a reference to Mizpah being the nearest provincial capital within the Persian administration of the region. This makes sense in itself, since the town of Mizpah was a centre of governance from Babylonian times (Jer 40:6).
But it does not constitute an easy translation of the verse. Let me show you a picture and suggest an alternative.
The Judgment Seat at the City Gate at Dan (far northern Israel)
I have seen a picture somewhere of a much higher seat, built into a city wall, but I can’t find it right now, so this will have to do.
I just wonder whether ‘kissēʾ‘ (‘seat’) here might be meant literally, not as a reference to Mizpah as the administrative centre, but denoting that part of Jerusalem’s wall that had such a facility for judgment and decree-making, for the use of the Persian administrator of the province of Aber-Naharaim, which covered Yehud (post-exilic Judah) when he happened to be in town. (Perhaps the preceding word, ‘hammiṣpâ‘, normally the name of the town, is being used in its general sense as an elevated place or ‘look-out’ here? It’s a long shot, perhaps.* Comments?)
The whole situation of the wall reconstruction was quite politically sensitive. It was important that the rebuilders remained clearly within the approved boundaries of Artaxerxes mandate to Nehemiah for the rebuilding. Even the (quite necessary) incorporation of a formal place of judgment and decree into the rebuilt Jerusalem would have expressed the returned exiles’ willingness to co-operate with the Persian administration, helping avoid the charge of “rebelling against the king” (Neh 2:19)
* On the Hebrew grammar concerning the town name Mizpah, ‘hammiṣpâ‘, it is interesting that many occurrences of this name feature the definite article, which is unusual for proper nouns in Hebrew, which don’t require the article but are inherently definite. In fact, Gesenius’ grammar (#125.1.a-d) makes it a rule that proper nouns do not have the article unless something has gone wrong. But most of the 49 occurrences of the name in the OT do have the article! Perhaps it was a carry-over from the time when it was a kind of geographical reference – “the watchtower” – and the article simply stuck. An analogy would be a suburb in Melbourne near where I live: ‘The Basin’.