It's not backbone. Age cards, enforcement, etc. takes manpower, time, money, etc. Look at the NCAA. It is hard for them to investigate/enforce all the rules.
Unfortunately, college coaches want to look at Rising 9th graders, so there is no push to go back to age based youth lacrosse (and many obviously support grade based because it helps with recruiting).
Its called integrity. Coaches can email in a list of players to USALAX with photos. An ID card is issued with the photo. Could take 15 min per team and interns do it. Not hard at all. It actually can be done while getting your USALAX number.
Play in year you were born, play up, but not play down. Its that easy. Don't care if you are going to re-class or PG you play in the year you were born. Youth Soccer and Men's League does it. There are over 3 Million registered youth soccer players compared to approximately 750,000 in youth lacrosse.
