In the United Kingdom, it’s a crime to advocate (in print) the abolition of the monarchy. Still on the books, though rarely enforced.
Treason Felony Act, 1848, s. 3
11 & 12 Vict. c. 12:
Offences declared felonies by this Act to be punishable by transportation or imprisonment.
If any person whatsoever shall, within the United Kingdom or without, compass, imagine, invent, devise, or intend to deprive or depose our Most Gracious Lady the Queen, from the style, honour, or royal name of the imperial crown of the United Kingdom, or of any other of her Majesty’s dominions and countries, or to levy war against her Majesty, within any part of the United Kingdom, in order by force or constraint to compel her to change her measures or counsels, or in order to put any force or constraint upon or in order to intimidate or overawe both Houses or either House of Parliament, or to move or stir any foreigner or stranger with force to invade the United Kingdom or any other of her Majesty’s dominions or countries under the obeisance of her Majesty, and such compassings, imaginations, inventions, devices, or intentions, or any of them, shall express, utter, or declare, by publishing any printing or writing . . . . . . F1 or by any overt act or deed, every person so offending shall be guilty of felony, and being convicted thereof shall be liable . . . . . . F2 to be transported beyond the seas for the term or his or her natural life . . . . . .
Modifications etc. (not altering text):
C1 Reference to transportation for life to be construed as reference to imprisonment for life or any shorter term: Penal Servitude Act 1857 (c. 3), s. 2, (E.W.) Criminal Justice Act 1948 (c. 58), s. 1(2) and (S.) Criminal Procedure (Scotland) Act 1975 (c. 21), s. 22(1)(2)