I think if we look again at the listing and wording for the Cameron of Lochiel tartan on the Clan website

"2) Cameron of Lochiel: This red and blue tartan is similar to that worn by the 18th Chief, Donald "The Gentle Lochiel" Cameron in a portrait hanging at Achnacarry. It was first illustrated in 1810 in Wilson's Collection. This is the personal tartan of the Chief and his immediate family; as a rule it should not be worn by clansfolk".

the wording does not mention either restricted or reserved, therefore I surmise from this that the tartan is neither. Only that it is generally accepted that the tartan, whilst technically available to all is accepted as being the personal tartan of the Lochiel and out of respect and convention should not be worn by clansfolk.

Its just not the done thing old bean.