"defy the authorities to upset such a large number of people and such a huge volume of business by declaring it illegal"

Question

I never served in the British Army. What does the emboldened phrase mean?

Who is the "corps"? Which people is Goode referring?

If "the rest of the corps" joined you, then which "large number of people and such a huge volume of business" are you upsetting?

Solely the political and legal authorities have the power to declare things illegal. What is being declared illegal?

As in the Army, there are two opposing but equally effective techniques to avoid bringing disaster on your head from on high. One is to keep out of the way, proceed in stealth and hope that no one will know you are there, still less what you are doing. The other is the exact opposite, namely to promote your activities with a fanfare of trumpets, persuade the rest of the corps to join you and then defy the authorities to upset such a large number of people and such a huge volume of business by declaring it illegal! In the international markets the latter technique seems to work rather well, always so long as one does not come up against a rural judge whose main interests lie in equity and the avoidance of unconscionable bargains!

I am quoting from Sealy and Hooley's Commercial Law 2020 6 edn, p 35 — that in turn quotes ‘The Codification of Commercial Law’ by RM Goode (1988) 14 Mon LR 135 at page 150.

Answer 1

Defy in this case is taking the slightly less common meaning of "challenge" or "dare" (third at this link) rather than "resist" or "disobey." This usage of defy is always structured "defy [someone] to [do something]."

The "large number of people" refers to the corps.

The speaker is saying that if the entire corps (i.e., the whole army, or a large division of it) joins in the activities, the authorities will not dare to upset the whole group by declaring their activities illegal.