I'm dubious of the security threat reasoning, because a variety of unions and workers all announced they wouldn't cooperate with the visit.

I know the tram drivers and other transport unions said they wouldn't operate for a Royal.

And then there's this gem:

CGT union announced this week that its members at Mobilier National, the institution in charge of providing flags, red carpets and furniture for public buildings, would not help prepare a Sunday reception for the king upon his arrival in Paris.