Or indeed can you even draw your magically enhanced sword from your belt without lowering your Parma ritual?
It seems to me that the new Parma, though much better protection, also rather wraps magi in too much cotton wool for their own good. My Troupe is still having this discussion (in between greedily eyeing up other covenant spell libraries) and one variation on the Parma rules might yet be adopted. I'd be interested to hear what others think, particularly if think there are 'exploits' that we haven't thought of.
The suggestion is that the Parma operates differently depending upon whether the magus initiates the action, or the magic object moves towards him.
If the magus initiates the action then the 'power of his will' or his 'specific intent' automatically overrides the Parma, allowing him to pick up magical items, draw magical swords, drink potions, ride magically created horses, etc
If the object moves towards him, then the Parma automatically resists it (if it's strong enough). Preventing it from reaching the magus. So he can't be hit by magical swords, be affected by magical liquids poured on him, be trampled by magically created horses, etc. This is also consistent with why a Maga can cross a magical bridge without slipping off (she intends to do so), but why a magical bridge will not harm her if it falls on her.
Side effect: Magi can inadvertantly bypass their Parma by intentionally touching things. So, if he deliberately touches the cursed stone - he gets the curse. Bonisagus created the Parma Magica to protect magi (i.e. the wise!) - so if a person is tricked or is too impetuous to think things through, that's just their misfortune.
The Parma does not have any understanding of when or why a magus might will an object through it. So, magical poisons may affect him if he lacks the caution to check for them - he intends to drink, but does not realise it is poison.
The Parma cannot be tricked, however, and so cannot be 'fooled' into allowing anything through that the magus did not intend to do. So, the fact that he is drinking that liquid does not allow any other liquid (cast while he is drinking) to automatically affect him.
Another example is if the magus is pushed into a pit of magical spikes - he may be moving towards them, but that was not his intention; so the Parma will attempt to resist the magic.
This idea only applies to magical objects - so a touch range spell still requires the Parma to be lowered before it affects.