Complex sentence: Furthmore, he barred the Noldor that followed the sons of Fëanor from entering his realm, but allowed entry those of the Houses of Fingolfin and Finarfin.
Split into simpler sentences: Furthmore, he barred the Noldor who followed the sons of Fëanor from entering his realm. He allowed entry to the Houses of Fingolfin and Finarfin.