No idea why you're all coming up with the 'rules' on here, as if you minority % of fans have some sort of influence when it comes to telling the majority how to behave ( you're just a few blokes on the internet!).
Ultimately, if enough people want to go on the pitch, there will be a pitch invasion.
I can't believe there are actually people sad enough to start posts about this sort of thing in advance tbh!
Who wakes up in the morning pondering the etiquette on whether Saints fans should or shouldn't invade the pitch his season? Strewth.