is a grammatically perfect sentence meaning:
"Permission is required for the unsheathing of 赤鍵."
(I presume 赤鍵 is read あかかげ, but since I could not be certain, I left it in kanji. The word must be a proper noun.)
「には」 cannot be used in place of 「に」 because 「は」 as a topic marker is already used in 「赤鍵は」. You cannot use it twice.
As you stated, 「～～には～～が必要」 is a common phrase and it can be used in the sentence in question only if the necessary alterations are made. That sentence will be:
The 「は」 in the original has been changed to 「の」 so that the topic marker 「は」 is used only once.
To use the 「～～には～～が必要」 construct correctly, you must place either a noun or a verb in the dictionary form right in front of the 「には」. 「赤鍵の抜刀」 is a noun phrase, so it works out fine.
What happens if you used two 「は's」 in this sentence?
This sentence is still actually correct and grammatical, but the meaning will change somewhat because now the 「は」 in 「には」 will be the constrastive marker. Thus, this new sentence means:
"Permission is required for the unsheathing of 赤鍵, (but it is not required for doing something else with 赤鍵.)"