Nemo me impune incessit
What does it mean? 
found at Wikipedia:
Nemo me impune lacessit
(English: No one wounds me with impunity, literally meaning (lacessere = to appeal to, to provoke, to attack): No one provokes me with impunity) is the royal Scottish motto, used historically for the Kingdom of Scotland where it appeared on the Royal Arms of Scotland. Today it is the motto the monarch of the United Kingdom uses when in Scotland, and it appears on the Royal coat of arms of the United Kingdom when in use in Scotland.
A more colloquial translation into English would be "No one attacks me and gets away with it." Similarly, in Scots this is usually rendered as "Wha daur meddle wi me? ", which more literally means "Who dares meddle with me?"
It is also the motto of the Order of the Thistle, the Scottish chivalrous order and of the British Army regiments The Royal Regiment of Scotland and Scots Guards. It was also the motto of the former Royal Scots, Royal Highland Fusiliers and Black Watch regiments.
The motto appears as an inscription on the rim of the 1984 and 1994 "Scottish" editions of the British One Pound coin and is also referenced in the Edgar Allan Poe story "The Cask of Amontillado" (Poe was adopted by a Scottish merchant).
