Laity out in the nave are not “admitted to the sacred liturgy” in that fashion, in canon law. The sacred liturgy is the stuff happening on the altar or at the lecterns. You could make a case for the choir, because we are clergy stand-ins. Nobody else. The laity in general “assist” at the sacred liturgy, and that is as far as it goes. The laity regulate themselves, other than things like “It is sacrilege to murder someone inside a church building.”
You want illegal gestures, that is where you find them - in the altar area… Not “thou shalt not sneeze twice in the pews.”
Argh. Clericalization of the laity – see where it leads? Madness. And breastfeeding posture regulations, probably, with diagrams of baby angles.
Back in the day, there was an instruction that at a Low Mass, the laity should kneel the whole time and say nothing, except when they stood to hear the Gospel. But it was only a guideline during Victorian times, might not have existed before then, and went away entirely in 1920.
The other guideline for laypeople was “do like the clergy do when they sit in choir ( ie, attend Mass in the pews).” But again, it was just a nice idea with no legal teeth.
Women sit on one side, men on the other? Nothing but a custom that the laity felt like doing, in some times and places. Do we want to do it now? No. The closest thing to a lay rubric was the hat regulations, and those went away. So why this craze to regulate our perpetual freedoms away? Because some people are bored?
If they want us to have rubrics, they can tonsure us and give us stipends.