When do regulations apply within airports and seaports?

The regulations apply if vehicles carrying dangerous goods use roads that are freely available for other road users.

A typical situation involves airport perimeter roads which may be owned by the airport but are public roads. If fuel depots are situated on those roads then the regulations apply to movements from there on to the airport proper (ie "airside").
In some cases, fuel terminals are within the airport itself, and only airport-authorised vehicles are allowed in those areas. In that case, CDG Regulations do not apply. If there are concerns about standards, other legislation is available to remedy the matter and in any case the airport operator is bound to have an interest.

Similar principles can be applied at seaports. CDG Regulations will apply if areas used by the public (for example to get to or queue for ferries) are used by refuelling tankers. Note that heavier fuel oils often used by ships may not be dangerous goods for the purposes of the regulations.