Ever since the FRC became the FCC in the 1930s, the FCC has regulated both wired and wireless communications in the USA. Their rules governed wired communications too. As I understand it, the Bell System was essentially a regulated monopoly, and as part of their monopoly, they had the power to approve or disapprove ALL connections to their lines. So amateur radio phone patches were indeed technically a violation of the rules unless authorized by the telcos. The way the telcos enforced the rules was to threaten disconnection. Since they were the only game in town, this could be a big problem. However, they tended to look the other way unless there was real $$ involved. Plus, when amateurs were running phone patches to Vietnam, it would not have looked good for Ma Bell to say "you can't do that!" - particularly since they couldn't offer the service themselves. Plus, many phone patches also involved long-distance calls on the Bell System anyway. ----- It took several Supreme Court rulings to break down the monopoly. First was the Hush-A-Phone case: https://en.wikipedia.org/wiki/Hush-A-Phone_Corp._v._United_States which wasn't even an electrical connection!. The Supremes ruled for Hush-A-Phone in 1956. The Hush-A-Phone device had been around since the 1920s, but its improved model resulted in the lawsuit. The improved model was developed by Leo Beranek, who is now 102 years old - and was a radio amateur (don't know if he still has a license). https://en.wikipedia.org/wiki/Leo_Beranek What really cracked the wall was the 1968 Carterfone Case, in which the Supremes ruled that the Telco restrictions were unreasonable and they had to make provision for interconnection. https://en.wikipedia.org/wiki/Carterfone which was reported in QST for September 1968. Then came MCI and Sprint and the breakup in 1984. IMHO, the Bell System had a good thing going, but held on too tightly, and ruined it for everyone. Had they been a little smarter, things would have been very different.