Recently, Dave A. posted:

Well, quite possibly because the FAA inspector was technically wrong.
Whether you're legal VFR or not depends on the conditions at your
point in space and time, not what some weather station several miles
away might be reporting.

The question was, what is a legal briefing and where is it stated in
the regulations. If you take off in the conditions stated by George
Patternson you are technically flying illegal.

Then, why do Pireps trump briefings? Whether one is "flying illegal" is
determined by the conditions where one is flying, not the conditions
elsewhere.

The philosophizing on the subject aside, all indications given by
the FAA is that the FSS and DUATS weather and NOTAMS are your only
proof should legal proceedings take place that you followed 91.103.

This is a somewhat different matter. Should one need such proof, FSS and
DUATS may be the only sources that are not to be challenged in court.
However, if you crash at a fogged-in airport because FSS and/or DUATS
report CAVU elsewhere, good luck trying to use those reports to defend
yourself.

Neil