This quote has been modified but, in doing so, the underlying intent may have been lost. Formerly, "Every ruler is harsh whose laws are new" states the political maxim later documented in Machiavelli's "The Prince" wherein the invading conqueror of any Principality would be wise not to change any laws or taxes, to minimise disaffection by the populace. This revised translation/quotation simply implies that ALL new rulers are harsh.
This is a great point. I've reverted it back to: "Every ruler is harsh whose laws are new."