I don't really understand how any of it would need to be phrase to hold up legally, but for me it would basically be something like this: Starting with the academic year (9/1) following your 18th birthday, any year of professional basketball counts as a year against your college eligibility.
Examples: (these assume the current 5-to-play-4 clock)
- You turned 18 on July 1st, you played pro ball the year before, you are enrolling at an NCAA school in August: Perfectly fine, you enter with the normal clock.
- You turned 20 on December 15th last year. You have been playing pro ball for the last three seasons: The year you turned 18 doesn't count, but the next two do (the season you went from 18 to 19, and the season you went from 19 to 20.) You enter with two remaining years of eligibility.
- You're 23 and planning to enroll this fall with a January birthday, you've been playing pro basketball since you were 17: all five of your professional seasons from age 18-23 count, you have exhausted all five years of your clock, and are not eligible.