[DmBarch]

Halachah (Jewish law) defines a Jew as one whose mother is Jewish, or who has converted according to religious law

I seem to remember that there was a need to better integrate the Orthodox into the rest of the country when the State of Israel was founded. One way to do this was to yield to their beliefs on conversions. To settle in Israel, a convert would have to do the Orthodox conversion process.

[Bella_Bru]

Actually, people who have Reform or Conservative conversions can return under the Law of Return, however they are not considered Jewish.