"Lèse majesté (French expression, from the Latin Laesa maiestas or Laesae maiestatis (crimen), (crime of) injury to the Majesty; in English, also lese majesty or leze majesty) is the crime of violating majesty, an offence against the dignity of a reigning sovereign or against a state.
This behaviour was first classified as a criminal offence against the dignity of the Roman republic in Ancient Rome. In time, as the Emperor became identified with the Roman state (the empire never formally became a monarchy), it was essentially applied to offences against his person.<1> Though legally the princeps civitatis (his official title, roughly 'first citizen') could never become a sovereign, as the republic was never abolished, emperors were to be deified as divus, first posthumously but ultimately while reigning, and thus enjoyed the legal protection provided for the divinities of the pagan state cult; by the time it was exchanged for Christianity, the monarchical tradition in all but name was well established (an example of the way the Roman religion was made to serve the political elite).
Narrower conceptions of offences against Majesty as offences against the crown predominated in the European kingdoms that emerged in the early mediaeval period. In feudal Europe, various real crimes were classified as lèse majesté even though not intentionally directed against the crown, such as counterfeiting because coins bear the monarch's effigy and/or coat of arms.
However, since the disappearance of absolute monarchy, this is viewed as less of a crime, although similar, more malicious acts, could be considered treason. By analogy, as modern times saw republics emerging as great powers, a similar crime may be constituted, though not under this name, by any offence against the highest representatives of any state ( e.g. all heads of state, regardless of their title, as in Belgium)."
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http://en.wikipedia.org/wiki/Lese-majeste>