Law and regulation are country-specific
Traditions, historical events such as foreign rule or liberation struggles, intellectual and religious developments and much more form locally different bases for the development of law in individual countries. This is why the legal situations in different countries, even if they are neighbouring, often differ considerably. The legal classification of nudity must therefore be considered on a country-specific basis.
General note
All considerations on the topic of "nudity and law" collected here have been carefully researched by making use of numerous sources (law, juridical comments concerning law, opinions, reasons for judgements etc.). However, the authors are not lawyers. Therefore, the subsequent overview cannot be considered as legally binding statements (if existing at all) and do not replace any legal advice.
Info about nude bathing in the world
For a first overview of the legal situation or naturist practice in many countries of the world, the website "Travel topics > Concerns > Naturism" (wikivoyage.org) might be useful.