that is excellent example. Since apparently everything was done 'by rules' but definitely not by the spirit of the rules there's not much USTA can do. In that case I think it is up to other teams' players and captains to make league play, well, uncomfortable for the offending participants.
First, teams playing in good spirit need to get together and agree on the approach. It may require giving up one season of play, but sometimes sacrifices need to be made. These days I would say public shaming, in a tactful way of course, does wonders. Few suggestions:
When you play the offending team or player you go by every single rule to the letter. You ask for score after each point to be announced loudly, sometimes twice. You check the height of the net after each set. You make sure there are singles sticks and if there are none you refuse to play. You ask for the net cord to be tightened. You warn him you will be looking for foot faults. You ask him every other point if he is sure the ball was out. You take sweet time on the changeovers. You take your time on your serve, and on the returns. You do not skimp on toweling off between points. If that happens _during every match against that team_ I think they will get the point.
Then I would also give the player and the captain an honorary award. Like before the match have your players line up, clapping, and you give that captain a starbucks gift card with a message 'to the captain for outstanding out of the box thinking making it possible for a 3 star junior player to play against overweight 40year fathers of two'. And to the player 'for extraordinary results since nothing impresses college coach/counselor more than beating up on players twice your age that were just promoted from 3.5 level.' These things get out, and I'm not sure if those juniors would be lining up to play next year.
p.s. we kind of did similar years ago when we were running a tournament for normal rec players and there was this dude signing up each year and winning with average score of 6:1 6:2. He was flirting with professional circuit when younger, and was clearly out of level. But, in his words, he has not played professionally in 5 years so he was technically eligible. He could have signed up for another category where college players (or soon to be) played - but he preferred to win at our rec level. So one year we all chipped in, bought some trophy from TJ Maxx, got all together before his first scheduled match, and handed him the trophy along with monetary award, and informed him that he won first place in a new category that was created for him 'for players exploiting loopholes to sign up for lower level category'. All while clapping, cheering, balloons, etc. He got the message.