It goes without saying, use of said frequency should be prohibited for other purposes, especially marketing.
Legally, use of horns in traffic is restricted, and abuse can be punished. Doesn’t keep people from honking all the time.
Tho I like the proposal to require that manufacturers design car horns to sound as loudly inside the cabin as outside. Might make a dent.
I myself pretty much never honk. I understand honking makes sense on narrow bendy roads like in the mountains, where you need to alert the drivers behind the corner, but I don't see any other legitimate reasons to be honest.
And of course there will always be fringe cases. What if I go to sleep with regular foam earplugs, what if I take a sleeping pill etc. Or what if the warning sound can't be engineered to fit a ANC friendly frequency, like somebody screaming, a car tire screech behind me and so on.
Also ANC works best on wide-spectrum sounds, so any kind of siren or the cries of a child will go through, as the spectrum is a series of narrow peaks.
And now you want to take that away too? No thanks. I get safety is important, but so is relief from noise pollution. Noise pollution is very damaging to your health. There needs to be a balance, and currently the safety police are weighing the scales inappropriately low.