I've read in this thread that a layover greater than 24 hours is not allowed. However, JAL website will allow a GMP-HND-LAX booking which has this layover if I booked for July 21.

I would book the GMP-HND flight with cash and keep my Alaska redemption for the HND-LAX leg, asking GMP check in staff to tag my luggage all the way to LAX.

Any confirmed/written policy suggesting this wouldn't work?