Practices that were once legal, tolerated or openly conducted have subsequently been prohibited in many parts of the world. However, laws vary significantly between countries, so something prohibited in one jurisdiction may still occur legally or illegally elsewhere.
Slavery Legal ownership of human beings existed across numerous societies for centuries.
Modern international law prohibits slavery. The United Nations Universal Declaration of Human Rights states that nobody shall be held in slavery or servitude, while international conventions have developed additional obligations concerning slavery and forced labour.
Illegal forced labour and human trafficking nevertheless remain worldwide problems.
Child Labour Children historically worked in mines, factories, agriculture and other dangerous occupations.
Today, international standards established through the International Labour Organization seek to eliminate the worst forms of child labour and establish minimum ages for employment.
The exact minimum working age and permitted jobs differ by country.
Dangerous Industrial Practices Workers in earlier industrial periods routinely encountered machinery, chemicals and working environments that would breach modern safety standards.
In the United States, the Occupational Safety and Health Administration sets federal workplace requirements. Britain's Health and Safety Executive performs a comparable regulatory role, while other countries operate their own systems.
Human Experimentation Without Proper Consent Modern research ethics developed partly in response to serious historical abuses.
The World Medical Association's Declaration of Helsinki establishes ethical principles for medical research involving human participants. National laws and regulatory systems add further requirements, meaning the precise approval and consent rules vary internationally.
Certain Weapons And Methods Of Warfare Warfare is also subject to restrictions that did not exist in earlier centuries.
The International Committee of the Red Cross traces modern international humanitarian law back to the first Geneva Convention of 1864. Subsequent treaties developed much broader protections for wounded combatants, prisoners and civilians.
International agreements now prohibit or restrict particular weapons and conduct, although which treaties legally bind a country depends partly on whether that state has joined them.
Looking at old photographs can therefore be startling: activities depicted openly in one era may violate criminal, employment, human-rights or humanitarian law today.