So far, Israel has decided to allow into Gaza all item except those fit for military use. What remains of the "siege" is allowing the Export of finished goods even if raw materials can come in, as well as movement of Gazans in and out of that territory (subject to security restrictions. The inability to export essentially destroys the Gaza economy, rendering the population destitute and in need of food relief. And here is a legal opinion (by the UN's Human Rights Council): "The [Goldstone] Report states that Israeli acts that deprive Palestinians in the Gaza Strip of their means of subsistence, employment, housing and water, that deny their freedom of movement and their right to leave and enter their own country, that limit their rights to access a court of law and an effective remedy, could lead a competent court to find that the crime of persecution, a crime against humanity, has been committed"- unhchr.ch/huricane/huricane.nsf/0/9B63490FFCBE44E5C1257632004EA67B?opendocument In any event, the prevention of ships going into Gaza is justified by security concerns. The ports of Ashdod (Israel) and El-Arish (Egypt) are near the Gaza strip and should be used instead.
Jordan foreign minister says to speak with Kerry on Israel-Palestinian conflict (Reuters)
from the article: Report: Lieberman changes policy, invites European diplomats to Gaza