The organisers of the flotillas (last year and this year) repeatedly declared that they would welcome an inspection by the UN or any other credible international organisation, at sea or at the port. They also declared that they would welcome UN to oversee the distribution of the aid. The activists' refusal to allow Israel to decide which items may go in or out is very understandable since Israel is collectively punishing the population of Gaza, which is totally illegal under international law. Israel has destroyed hundreds of homes and now blocking the building supplies required to rebuild them. Israel is also blocking items like chocolate, pasta, chewing gum, medical supplies - which is just... silly.
UN to hold off on separate Afghan bombing probe for now (Reuters)
from the article: Israel prepping to block next Gaza flotilla