Nothing new, but this is from the American Heraldry Society website:
The Lord Lyon King of Arms is empowered under Scottish law to grant arms to “virtuous and well-deserving” persons. Lord Lyon interprets his jurisdiction to include anyone domiciled in Scotland, as well as any person domiciled in the United Kingdom or in an overseas realm of the Commonwealth who is not of English, Welsh, or Irish descent. By virtue of his power to grant arms posthumously upon petition of a deceased person’s heirs, Lyon can also grant arms to anyone who can prove descent in the direct male line from someone living within a previous Lyon’s jurisdiction. This includes Americans of Scottish ancestry whose male-line ancestors were in the 13 colonies prior to 1783. There are certain other circumstances in which a grant to someone neither of Scottish birth nor domiciled in Scotland may be eligible, but they are rare and would be up to the judgment of Lord Lyon himself. As of 1 April 2010, the fee for a new grant of personal arms with shield and crest is £2,081, which includes an illuminated vellum certificate (letters patent). As indicated above, Americans are normally granted arms in memory of an ancestor; this route usually requires that the arms also be matriculated for the applicant’s own use for an additional fee. Armorial bearings are protected by law in Scotland and it is illegal to use arms there unless they have been granted by Lord Lyon or matriculated in Lyon Court.
If you are a member of a chivalric order of which HM the Queen is the head (i.e. the Most Venerable Order of St. John of Jerusalem), the College of Arms will grant honorary arms regardless of whether or not you meet the descendent requirements. It is possible, though I do not know, that Lyon will do the same. Keep in mind that all grants from the College are honorary for non-British citizens, while all grants from Lyon are substantive regardless of citizenship so the College may tow a different line in that regard.