Existing behavior: Both opcodes 146 (cast spell at creature) and 148 (cast spell at point) are unaffected by dead magic (when opcode 60 is used and param2 = 3/4/5) even if param2 of opcode 146/148 is set to 0 (casting type = normal). In that way, you could fire off spells from scrolls in dead magic areas.
Expected behavior: scrolls would be affected by dead magic and fail to cast. More literally, if param2 of opcode 60 is set to 3, 4 or 5, then it affects spells cast via opcodes 146 and 148 if their param2 is set to 0 (cast normally). On the other hand, if param2 of opcodes 146 and 148 are set to 1 (cast instantly) then that shouldn't be affected by dead magic.
How to reproduce this: CLUA yourself to AR3004 and attempt to use any spell scroll.