Every time this comes up I ask what rule and never get an answer!!
As far as I can make out clubs are only required to provide all seated stadium not that people need to sit in the seats.
Although SPL rule H7.5 states "The Home Club in any Official Match must ensure, so far as is reasonably practicable, (i) good order and security;", heavy handed stewarding would actually break this rule, so telling your stewards not to wade in is actually following the rules!!