I believe it is still a plural use of Scots i.e. The law of the Scots. "Scots mayor" is in this case is not referring a mayor of Scotland but an individual who is Scottish and happens to be a major. Just seems off. But the writer is German so no worries.
And I'm not trying to be a Scots Inquisition, just interested in language usage :-)
Or a Scotch Inquisition - which is what happens to you if you put Coca Cola in a malt.