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[MacMillan of Rathdown]

This is nonsense, if I want to have salmon buttons on my waistcoat, jacket, or anywhere else, I can do, simple as that.
If I am copying exactly an image of a particular salmon that someone else has the rights to, that of course is something else. If I am trying to pass myself off as someone else by the use of some decorative device ,that too is wrong.

as Matt said :
I wonder if this is just a "stongly expressed opinion." I mean, what jurisdiction does the Lyon Court have over non-heraldic dress and accessories, really?

The simple answer is that it doesn't have any jurisdiction.

If anyone of us want to use artistic and/or decorative images as buttons or decoration, then we may. Of course some may question taste or style, but there is no "law" to prevent us

Paul, I am sorry to say that your assessment of Scots Law and the Scottish Law Courts and their jurisdiction is flat out wrong.

Actually, there is a law* to prevent one usurping the heraldic rights of others, and while the jurisdiction of that law may be limited to the geographic entity of Scotland, it none the less exists. Were one to flaunt the law in Scotland one could very well find oneself hauled before the Court of the Lord Lyon and not only fined, but the offending article would be taken away and defaced.

Now it is true that the offense can only occur if the design (in this instance salmon buttons) is so similar to that of the badge of Argyll that, to the average man, they would appear to be the same. If the attitude of the salmon (the posture in which it is depicted) is different (leaping, as opposed to stretched out as though being served on a platter) then one could probably successfully argue that no offense has been committed, and in all likelihood the Court would agree. But that final decision would be up to the Court, who has absolute jurisdiction in these matters.

You may think it nonsense in London, but it is the law in Scotland.

*Statute 1596, cap. 125, and 1672, cap. 47, and 1669, cap. 95 clearly spell out the authority and jurisdiction of the Court of the Lord Lyon.