The phrase 'then prevailing' is correct and usable in written English.
It can be used to refer to something that was taking place at a certain point in the past. For example: "The then prevailing economic conditions put a lot of small businesses out of business."
He judged that, under the conditions then prevailing, Russia had best keep its traditional institutions.
It had a corrugated iron roof and, in the midsummer temperatures then prevailing, was like an oven.
Because they lacked precedence under the rules then prevailing, however, the Soviet Union reverted to the previously used titles.
The evidence is clear that in 1955 defendant was warned of his constitutional rights in accordance with the requirements then prevailing.' State v. Lewis, 1 N.C.App.
The A-family of scenarios emerged as the most likely outcome, but it varied sharply from the implicit worldview then prevailing at Shell.
Appalled at the low level of literacy then prevailing in Indiana, Mills began a one-man crusade to bring about the creation of a state public-school system.
These opinions reflect the then-prevailing philosophy of economic due process which has since been repudiated.
In essence, this movement was a powerful rejection of then-prevailing photographic conventions.
His work tended to document the dynamic acculturation theories of Radcliffe-Brown over Malinowski's then-prevailing ahistorical model.
"When it set down a federal labor policy Congress plainly meant to do more than simply to alter the then-prevailing substantive law.
Respondent's trial and appeals were, at the time they occurred, conducted in a manner perfectly consistent with then-prevailing constitutional norms.
