It's come up in our saga to ask if spells can be detected through a Parma.
Case 1: Magus A may be under a spell and is unconscious. Magus B wants to know and, throwing the Code to the wind, casts an Intelligo Vim spell to directly probe Magus A. This either penetrates the Parma (success) or doesn't (failure). That's the usual understanding.
Case B: Maga Una may be under a spell. Maga Seconda wants to know and via vastly powerful and unlikely spontaneous magic, changes her own senses to detect magic, with the idea that magical effects emit species that ordinary mundane senses usually cannot perceive. If such species exist (to which I ask ?) would Seconda be able to detect an active magic effect through the Parma.
Yes, Seconda could wait until the Parma expires, but there is a time pressure.
It occurs to me the easiest sense to affect is probably to taste Maga Una, which is fairly amusing, but this brings up the question of direct contact with the cloaked-in-Parma maga.