Charms against Magic

While poking through 4th Edition I saw the rules for Charms against Magic in the Lab section. Are these still doable or have them been stricken from the realms :smiley:

For those without the text in front of them:

Even though there is no spell to do so, magi can invent magic devices (invested or lesser enchanted) to protect the bearer against magic. The effect uses the Arts Rego and Vim, and the level of the effect it equal to the Magic Resistance it provides. The charm works continually on the bearer of the device (though Constant Use* must still be chosen for the effect frequency). The effect works like the Parma Magica, but is incompatible with Parma Magica or any other type of magic resistance. Thus, the bearer may not add his score in a Form to the charm's Magic Reisitance. If the bearer has a Magic Resistance of his own, the higher of the two protections, that of the bearer or that of the charm, overrules the other.

*Now the Championesque "Always on".

Some problems I see are that this seems like an awefull powerful effect, akin to Parma Magica. Perhaps half the effect should be the MR.

There would be warping.

Shouldn't this have to penetrate someone's exhisting MR to affect them?

Items granting universal MR have been removed, on purpose, to increase the importance of Parma Magica. They have been reintroduced, in a limited way, as an example of a potential breakthrough in the Bonisagus chapter of HoH:TL. As such, they are entirely optional.

You can create items with ReVi or PeVi effect offering some sort of protection against magic, but it isn't really Magic Resistance.