Complex sentence: In the 1950s, Rufeisen applied for Israeli citizenship under the Law of Return, which provides Jews (and other) with Israeli citizenship through a streamlined naturalisation process (e.g. without the requirement of several years residency).
Split into simpler sentences: In the 1950s, Rufeisen attempted to apply for Israeli citizenship under the "Law of Return". This provides Jews with Israeli citizenship without having to go through the normal channels of naturalisation (e.g. the requirement of several years residency).