"With the end of the war [WWI] came another problem: the Radio Communication Act of 1912 was again in effect. This act provided that the government would guarantee the secrecy of communications:
No person or persons engaged in or having knowledge of the operation of any station or stations shall divulge or publish the contents of any messages transmitted or received by such station, except to the person or persons to whom the same may be directed, or their authorized agent, or to another station employed to forward such message to its destination, unless legally required to do so by the court of competent jurisdiction or other competent authority.
The law had been enacted after the proclamation of the International Radio-Telegraph Convention of July 8, 1912. Three days earlier, the United States had joined a great many other nations in London in affixing their signatures to the document. This was a very significant step for the United States, since it represented the first international convention of its type to which the country had adhered. To the Black Chamber, however, it represented a large obstacle that had to be overcome--illegally, if necessary.
By the time Yardley returned to the United States in April, 1919, the State Department was already busy trying to establish a secret liaison with the Western Union Telegraph Company. It was hoped that Western Union would cooperate with the Black Chamber in providing copies of needed messages. For six months the State Department got nowhere; the Radio Communication Act provided harsh penalties for any employee of a telegraph company who divulged the contents of a message. Then Yardley suggested to General Churchill [director of Military Intelligence] that he personally visit Western Union's president, Newcomb Carlton. The meeting was arranged in September, and Churchill, accompanied by Yardley, raised with President Carlton the delicate matter of his secretly supplying the Chamber, in total violation of the law, copies of all necessary telegrams. After the men 'had put all our cards on the table,' Yardley would later write, 'President Carlton seemed anxious to do everything he could for us.'
Under the agreed-on arrangements, a messenger called at Western Union's Washington office each morning and took the telegrams to the office of the Military Intelligence Division in Washington. They were returned to Western Union before the close of the same day.
In the spring of 1920 the Black Chamber began approaching the other major telegraph company, Postal Telegraph, with the same request...by the end of 1920 the Black Chamber had the secret and illegal cooperation of almost the entire American cable industry." (pp. 27-29)