Scots and English Law differ in various ways, one being the Law of Arms.
Scottish coats of arms are required to be matriculated at the Court of Lord Lyon, qv:
http://www.scotcourts.gov.uk/tribunals/lordlyon.asp

David Sellar is the present Lord Lyon King of Arms, qv:      
 http://www.law.ed.ac.uk/staff/wdavidhsellar_71.aspx

Further information can be seen at:   
 http://www.scotarmigers.net

Official Scottish Clans and Families
http://www.electricscotland.com/webclans/clanmenu.htm