As for your Ministry of Propaganda request for a citation of International Law, it is the "body of consensual principles which have evolved from customs and practices civilized nations utilize in regulating their relationships and such customs have great moral force. Zenith Radio Corp. v. Matshshita Elec. Indus. Co., Ltd., D.C.Pa., 494 F.Supp. 1161, 1178. International customs and treaties are generally considered to be the two most important sources of international law." Black's Law Dictionary, 6th Ed.
I am certain you know full well that International Law is not codified for citation in the same manner as U.S. Federal Law. Nevertheless, the civilized world recognizes, and has recognized its existence, for many, many years.
Mr. Spence hit it right off the bat when he wrote, "Secession, if lawful...". One side of the equation held that the southern acts were not lawful so the offer to pay, if it ever was made, would be moot. The first side had no interest in selling. It can also be argued that since the British government never recognized confederate sovereignty then they did not consider the secession lawful either.
The impression exists, that the people of the South proposed, from the first, to pay for all Federal property, and sent commissioners to Washington to arrange this.
That can be argued. The commissioners were sent to obtain recognition from the Lincoln government, and only once that was obtained to negotiate on issues of disagreement. Without the first condition being acceptable then the second part of the instructions are meaningless.
As for your Ministry of Propaganda request for a citation of International Law...
Don't have one, do you? Hence the lame attempt at insult.
OK, perhaps you can tell us what precedent guided the international law clause that you cannot state? And a precedent from the 'WTBS' (War The Between States?) era might be more applicable than one involving two 20th century electronics firms.