Are naval blockades legal?

Israel has had a long standing naval blockade along the coast of Gaza to ensure the Hamas there do not import arms that they would use against Israel.  Is this legit?  There seems to be popular uproar, especially when Israel enforced the blockade on May 31st with a senseless raid.

Was our blockade of Cuba in 1962 legit?

I might as well simply quote the wikipedia article:

According to the San Remo Manual on International Law Applicable to Armed Conflicts at Sea, 12 June 1994, a blockade is a legal method of warfare at sea, but is governed by rules. The blockading nation must publish a list of contraband. The manual describes what can never be contraband. Outside this list, the blockading nation is free to select anything as contraband. The blockading nation typically establish a blockaded area of water, but any ship can be inspected as soon as it is established that it is attempting to break the blockade. This inspection can occur inside the blockaded area or in international waters, but never inside the territorial waters of a neutral nation. A neutral ship must obey a request to stop for inspection from the blockading nation. If the situation so demands, the blockading nation can request that the ship divert to a known place or harbour for inspection. If the ship does not stop, then the ship is subject to capture. If people aboard the ship are resisting capture, they can be attacked. It is still not allowed to sink the ship, unless provision is made for rescueing the crew. Leaving the crew in liferafts / lifeboats does not constitue rescue. If a neutral ship is captured, any member of the crew, resisting capture can be treated as prisoners-of-war, while the remainder of the crew should be released. A neutral nation may choose to send a convoy accompanied by warships. The warship can provide guarantees that the convoy does not contain contraband. in which case, the blockading nation does not have any right of inspection.

Seems like they are legit, at least as far as International Law is concerned.

BTW, did you see the video?  Who is beating whom?