Based on Zionist principles, the law was intended to ensure that the State of Israel would be a Jewish state and a home for the Jewish people.
The law was later amended twice. The first time was on August 23, 1954, under then-prime minister Moshe Sharett, when a provision was added to deny citizenship to certain people, such as those with a criminal record.
The second change was more significant and on March 10, 1970 under then-prime minister Golda Meir, the law expanded the Right of Return to those who were not deemed Jewish according to Orthodox halacha definition, but also to those who were married to a Jew, converts to Judaism, or the grandchild of someone who was Jewish. Those not eligible for citizenship, however, were those who converted to another religion despite still being Jewish according to Halacha and, following a 1989 High Court of Justice ruling, Messianic Jews, as long as they don't have Jewish ancestry.
The reason for expanding the definition of being Jewish remains in dispute such as the "Who is a Jew?" argument that Israeli politicians and rabbinical authorities have debated continually throughout history. One notable point of dispute over the expansion was that it referred to similar criteria used by the Nazis during the Holocaust. They, of course, did not follow Halacha when determining if somebody was Jewish.Another much more recent change came through a High Court ruling this year, when it was determined that Reform and Conservative conversions carried out in Israel would make a convert eligible for citizenship under the Law of Return. Until that point, only those converting through Reform and Conservatives movements outside of Israel were eligible.
The Law of Return continues to enjoy broad support among Jews in Israel today, with a 2016 Pew poll finding that 98% of Israeli Jews wanted it to continue. It nevertheless remains a subject of considerable controversy, with some on the Right wanting to limit it because they believed many, including immigrants from the former Soviet Union gained citizenship despite not being halachically Jewish, and some on the Left who feel it is discriminatory against Arabs and Palestinians, who are denied an equivalent law.
Israel is not the only country with a Right of Return. In fact, the principle is very old, and a variant can even be found in the Magna Carta signed by King John of England in 1215.
Today, several countries possess active laws granting a Right of Return, including Armenia, Finland, who grant citizenship to those with ancestry, and Liberia, which grants citizenship to anyone of African descent.
But three countries that give right of return especially for Jews are , Portugal, Spain and Germany. The former two grant citizenship to Sephardi Jews if they can prove that they are descended from Jews expelled from the Iberian peninsula in 1492.
Germany has, for years, had a Basic Law to grant citizenship to those who lost their citizenship to the Nazis between 1933-1945 and their descendants. Often, however, many applicants were rejected because there were several loopholes in the legislation but last month, the Bundestag approved changes making it easier for descendants of those who fled the Nazis to obtain citizenship.