Ok so it says in the fluff that fomori can use magic as well as being resistant to magic. However they are listed as having arcane arrester in RC which by RAW automatically disallows magic usage.... which is it or has this been errattad?
pg 56 RC
Another peculiarity of the fomori metavariant is exposed by
British Administrative Bureau statistics which indicate a higher
than average incidence of magical talent among the fomorian population
(as much as 4% higher). A controlled study undertaken by
the Oxford Royal College of Thaumaturgy in 2048, however, indicates
that fomori seem to be demonstrably more resistant to spell
effects and magical powers than the average metahuman (with the
possible exception of gnomes). The mechanisms and reasons (both
genetic and evolutionary) for these apparently contradictory traits
are still unknown.
pg 111 RC
Arcane Arrester
Cost: 25 BP
When affected by a spell (including a critter’s Innate Spells),
the character—and she alone—treats Force-based effects (damage,
paralysis, etc.) at half (round down) actual strength. Note that the
actual Force of the spell is not actually reduced. For instance, a
character with Arcane Arrester targeted by a Force 5 spell would
resist it as if it were a Force 2 spell, though the spellcaster could
still add hits to improve the effect. Arcane Arrester cannot be
combined with Magic Resistance (p. 79, SR4). This quality can
be taken by characters with a Magic attribute.