As far as I am aware the point of registering a squad is that you can pick anybody at all from your first team squad. If you can't, then why are they in the first team squad? The RFL has no role in team selection. Saints can play whoever they want, whenever they want. Who are the RFL to rule on what is Saints' (or anyone's) "strongest team", and anyway where is the rule that says the "strongest team" has to be selected?
Of course, you can call it disrespectful or whatever, like when Saints fielded the reserves against Bradford and cost us a fortune at the gate, but if the other clubs have a problem with it, then they need to address it amongst themselves. Personally I hope they do it every week and finish last. It bit them on the arrse today, but seemingly they only lost because Charnley missed a sitter of a goal, which his gran could have backheeled over. IF he'd kicked it, and Wigan won, then it would clearly be impossible to say they should have played a stronger team. And totally impossible to "fine" them.
What you're really saying is Wigan should be fined or whatever if they lose to Widnes. And it's nonsense.