Several countries have laws against Holocaust denial. Such laws typically punish people who seriously minimise the scale of Nazi crimes, or entirely deny that generally accepted Nazi atrocities took place. The Wikipedia page lists several examples.
In Austria, National Socialism Prohibition Law (1947, amendments of 1992) section 3h criminalizes "whoever denies, grossly plays down, approves or tries to excuse the National Socialist genocide or other National Socialist crimes against humanity in a print publication, in broadcast or other media."
Belgium also has a 1995 law against those who "grossly minimise, attempts to justify, or approves the genocide committed by the German National Socialist Regime during the Second World War", punishable by "a prison sentence of eight days to one year, and by a fine of twenty six francs to five thousand francs".
In Czechia it is forbidden not only to deny Nazi genocide and crimes against humanity, but also similar crimes by Communist regimes (presumably primarily aimed at the Communist rulers in Czechoslovakia, the Soviet Union, and elsewhere in Eastern Europe). The Law Against Support and Dissemination of Movements Oppressing Human Rights and Freedoms (2001) § 405 says "Anyone who publicly denies, disputes, approves or attempts to justify a Nazi, Communist or other genocide or Nazi, Communist or other crimes against humanity or war crimes or crimes against peace will be punished by imprisonment for six months to three years".