Allowed by whom is the question.
Unfortunately, there is no real system to make sure that countries act in the best interests of all of their citizens. Killing Jews and other minorities was a common safety-valve mechanism throughout history of various rulers who allowed their people to vent their frustrations by killing the minorities who were supposedly causing problems. In most cases, the people are too stupid or too enraged to realize that it is the government's inefficiences and inequalities that are causing their ills.
It was only in the modern era that the idea that a citizen of any state is endowed with Rights to which he can appeal beyond the ability of the government to endorse or retract. It is only in this period, in those countries that believe that every human is truly endowed with equal rights (as opposed to just saying that), that the killing of Jews has been prohibited.
The United Nations is designed more as an international roundtable for countries to discuss policy and has very minimal powers to actual enforce any resolutions it seeks to implement. Additionally, many of the countries in the United Nations realize that any precedent set in the United Nations for violating national sovereignty (including in cases of genocide) could eventually be used to justify incursions in their nation and violations of their national sovereignty. As a result, the United Nations rarely even gets to a vote on questions of military intervention where the countries to be intervened in do not sanction UN involvement (which is always the case during genocides).
because Hitler was a Fat idiot! and he didnt like homosexuals or big groups and decided to kill them!
The Genocides was created in 1965.
The Genocides has 143 pages.
Yes, there have been multiple genocides after the Holocaust.
There have been genocides in 42+ countries. Here are a few: guatemala, rwanda, and cambodia.
Yes, genocides have happened in places such as Rwanda and Cambodia.
Genocides have been happening throughout human history, from ancient times, up to modern times, so it has been happening in many, many years.
The Holocaust can never happen again. The establishment of the state of Israel has ensured that. However genocides, some arguably worse, continue to this day.
Because you're adopted
Yes
To stop them happening again
It depends on the genocide. There are some genocides, like the East Timor Genocide, that the UN did help to stop. There are some genocides, like the Rwanda Genocide, that the UN ignored. There are some genocides like the Holocaust, which occurred prior to the UN's existence.
yes