Which restroom?
 

On an AA flight this afternoon, the announcements while taxiing included something close to the following:

"On our plane, there is one lavatory in the first class section of the plane and two lavatories in the rear. FAA regulations require that passengers use the lavatory in the section of the plane in which they are seated."

My (relatively trivial) question is whether such a matter is actually addressed in FAA regs? (The FA was very specific that it was an FAA regulation matter.)

My suspicion is that any such policy is just an airline policy, primarily for the courtesy of its F pax. Before the barrage hits, I am not suggesting that the F pax should not be entitled to such a courtesy. I just can't imagine the FAA putting forth such a regulation, with all the exceptions that would be needed (facilities in back (or front) out of order, limited mobility pax in front of coach, carts blocking aisle, etc.). If this is not actually an FAA reg, it seems inappropriate (to be very gentle) for this or any airline policy to be described to pax as an FAA reg.

Such a regulation would also seem to pose difficulties for single class planes (a la JetBlue, Southwest, Ted, Midwest, Frontier, etc.) in deciding which rows are allowed to use which restroom.

Thoughts?

A crew instruction becomes the "FAA reg" as failure to comply with crew instructions becomes the issue.