Legolas is free to go anytime he wants. Unlike Arwen ,he has a permanent
invitation to Valinor over the sea. In fact, he is a distant relative of King
Olwe of the Teleri.
he builds his ship in his Elf-realm of Ithillien, under his own authority. he
doesn't even bother looking for Cirdan.
Arwen is practically human now-no human can sail on an elf-boat without direct
permission from the Valar. Tuor and Earendil both did so and became immortal,
but Arwen has gone the other way and become mortal.
Look at the disaster at Dol Amroth- Amroth's ship somehow makes it through the
storm, but all the Numenorean ships, arguably bigger and mightier snap in two
or are wrecked. Elf ships are special, and Arwen forfieted the right to sail on
one the moment she chose mortality. No ship will bear her to Valinor,because no
ship will bear a human to
valinor.
There is but one task remaining in Arda-we,the Dragons of Valinor will make it happen.
Lone resident of the Republic of Gondor
PO-TA-TOE-S not PO -TAH-TOE-S!
