One of the correct options, in my opinion:
It is forbidden to use spell scrolls of levels 4 and 5 without having a corresponding level of the Mage Guild (MG) built in any of your castles, or it is necessary to comply with subparagraphs a and c of paragraph 5.2.
I agree, colleague :cool: :D, it can also be done this way, i.e., instead of the condition "If there is no corresponding level of MG in the starting castle, then..." use a disjunction ("or").
The fact that this clause refers to another rule is quite normal and is called an analogy of "law".