@Tigerlily They are actually very strict rules now!
Every Tuesday at 4.00pm Sydney time, each club will announce a 21-man squad consisting of 17 “Active” players named in position, with a maximum of four additional players named as “Reserves”. (The Warriors squad will be released at 3.00pm Sydney time [5.00pm Auckland time] on Tuesdays.)
Then 24 hours before each game kicks off a 19-man squad, only from players included in the initial 21-man squad, is selected with 17 “Active” players named in position and a maximum of two additional players named as “Reserves”.
Then one hour prior to kick-off a final team of 17 active players is confirmed, only selected from players included in the 19-man squad.
Clubs wanting to bring in a player from outside the 21-man squad or the 19-man squad after they have been announced must apply for an exemption which will be evaluated by the NRL’s Head of Football on a case-by-case basis.