Paul Lynch wrote:

Don't forget, the AIM is not regulatory. It is an informational source.
You can't violate it. You can violate 91.185.

That isn't quite correct. Some of the information in the AIM is informational.
But, some of it is directive and expands upon regulatory requirements. There
have been many enforcement actions under FAR 91.13 for failure to adhere to
directive language in the AIM.

The introduction to the AIM reads:

"This manual is designed to provide the aviation community with basic flight
information and ATC procedures for use in the National Airspace System (NAS) of
the United States. An international version called the Aeronautical Information
Publication contains parallel information, as well as specific information on
the international airports for use by the international community.

This manual contains the fundamentals required in order to fly in the United
States NAS. It also contains items of interest to pilots concerning health and
medical facts, factors affecting flight safety, a pilot/controller glossary of
terms used in the ATC System, and information on safety, accident, and hazard
reporting."

Note the second paragraph about "required fundamentals" and also "items of
interest."

An example is the additional reporting requirements listed in the AIM:

"5-3-3. Additional Reports
a. The following reports should be made to ATC or FSS facilities without a
specific ATC request:
1. At all times.
(a) When vacating any previously assigned altitude or flight level for a newly
assigned altitude or flight level.
(b) When an altitude change will be made if operating on a clearance specifying
VFR-on-top.
(c) When unable to climb/descend at a rate of a least 500 feet per minute.
(d) When approach has been missed. (Request clearance for specific action; i.e.,
to alternative airport, another approach, etc.)
(e) Change in the average true airspeed (at cruising altitude) when it varies by
5 percent or 10 knots (whichever is greater) from that filed in the flight plan.

(f) The time and altitude or flight level upon reaching a holding fix or point
to which cleared.
(g) When leaving any assigned holding fix or point."

Failure to make one of those reports has resulted in enforcement proceedings
under 91.13 and 91.183 (c) many times over the years. The fact that 5-3-3 a
says "should" is only because the FAA legal folks have consistently held that
use of the word "shall" for such passages in the AIM would constitute
rule-making, per se. Then, they would have to run every change to the AIM
through the complete NPRM process. No country does that under the ICAO rules
for its AIP (which the AIM is a domestic version of the United State's AIP.

"Should" works with the effect of regulation when coupled (in this case) with
91.183 (c), which is in accordance with ICAO international conventions.