Perhaps register was the wrong word
but the new to NPPL this season teams were pushed to sign up their players and purchase an annual or temp NPPL I.D. card. And you're right, nobody ever checked.
My point was isn't the ostensible purpose of the I.D. to control and/or regulate movement of players across teams and categories in the interests of "fairness"? And if not it's really nothing but another money-making scheme.