Parsing a humble form expression (maybe)

Question

その鞄は機内へのお持ち込みはできません
You cannot bring that bag on board

I'm struggling to understand the grammar of this sentence. I'm aware that you can make the humble form of a verb by adding an お onto the masu-stem and then adding する. I assumed that is what was going on here. So we have 持ち込む --> お持ち込みする

Turning する into できる seems okay to make the potential form. But then we also seem to be treating the お持ち込み as an independent noun. I'm happy that masu-stems can be used as nouns but what's troubling me is that none of that humble form structure we made has remained unscathed. In a plain sentence I would have just said 機内に持ち込むことができない (is that okay?).

I'm happy with the への part (田中への手紙 etc) but I don't understand why it is necessary here. Why not simply 機内にお持ち込みはできません as in my plain example?

I guess I'm also nervous about the は in the middle of お持ち込みはできません. It makes me think that may my analysis of it being the humble verb form is completely wrong.

Anyway I'm rambling now. The bottom line is that I have no idea how to parse this sentence correctly. Could someone please explain the grammar and provide some additional simple examples?

Answer 1

First of all, you don’t use a humble form to refer to something a customer does. So, that お持ち込み was not part of a humble form absorbed into a preceding noun phrase, to begin with. You should treat it like any other noun with a politeness or honorific prefix お, such as お食事.

Then, the sentence must start looking not much different from a sentence like:

こちらでのお食事はできません。

の is necessary here in order for こちらで to modify お食事 to form a noun phrase. The の in 機内へのお持ち込み is necessary for the same reason. The reason it has to be へ, instead of に, is that にの is not a valid combination.

By the way, the corresponding honorific form is お持ち込みになる.

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[Clarification]

機内へお持ち込みはできません and 機内にお持ち込みはできません are both as valid as こちらでお食事はできません. If you want to make it a noun phrase, you need の and の doesn’t go well with に.