This is what Wikipedia has to say about wearing the Scottish National Dress to a white tie event:

Scottish Highland dress

As a specific example of national dress, Scottish Highland dress may also be worn at white tie events.

The traditional white tie version of Highland dress consists of:

* Black formal kilt jacket - the Prince Charlie coatee, Montrose doublet, Sheriffmuir doublet, Kenmore doublet or regulation doublet is suitable
* Black barathea (or velvet, with a velvet doublet) or white piqué waistcoat; no waistcoat is worn with the Kenmore doublet
* Kilt
* White piqué shirt with white studs and cufflinks
* White piqué bow tie with the coatee or regulation doublet; white lace jabot with the other doublets
* Black Ghillie brogues; black buckle brogues ("Mary Janes") may be worn with the Montrose, Sheriffmuir, or Kenmore doublet
* Tartan or red and white, red and black or blue and white diced kilt hose
* Flashes
* Sporran - formal type with a silver-mounted cantle-top and fur pouch or a full fur and animal mask type