In reply to tistimetogo:
From speaking to people locally it sounds like the gendarmes were using common sense in looking at how well-equipped people were and asking them about their plans to determine who should be able to pass without a hut reservation if they were up and down in a day. From the initial news report about the extension:
'The restrictions were initially proposed to be in place for a week, but will now be enforced until August 1st, according to a French news report. During this period, access to the summit of Mont Blanc via this route, beyond the Tête-Rousse Glacier, is only granted to those who can provide evidence of a reservation at the Goûter refuge. Details of the restriction is provided in French on the Goûter refuge website (PDF at top).'
Not sure about bivvying.