Israeli enforcement of blockade draws condemnation, but it wasn't "piracy"

So, Israel maintains a well-known blockade of Gaza and it enforces that blockade because some ships in the past have been known to smuggle weapons into Gaza. These weapons are, of course, used to attack Israel. Such attacks, in turn, prompt more interference by Israel with Gaza's internal affairs...

Now, once again employing their most dangerous weapon - favorable press coverage - attempted Gaza blockade runners have found themselves bloodied by an Israeli naval force and got the UN to act: UN condemns Israel for attack on aid convoy:

Pressure on Israel to lift its blockade of Gaza increased further last night as the UN Security Council demanded a probe into the deadly attack on civilian aid ships in international waters. A Turkish charity in Gaza said that 19 people were missing; Israel put the death toll at 9.

As outrage grew over Israel’s attack on the flotilla of mostly Turkish aid vessels bound for Gaza, Security Council members, who had broken off from their spring holiday to hold an emergency session called for a “prompt, impartial, credible, transparent” investigation into the incident, and the release of all civilians being held by the Israelis.

Israel was called on to explain its use of “disproportionate force” against the humanitarian workers and Ban Ki Moon, the UN Secretary-General, said that he was shocked by the killings and demanded answers urgently.

Riyad Mansour, the Palestinian UN observer, called the attack on unarmed civilians on board foreign ships in international waters a “war crime,” and said it would not stop more ships from attempting to deliver aid to Gaza.

“Those fleets, one after the other, will be coming until the unethical blockade is put to an end and the suffering stops for our people,” he said.

While criticism of the vigor of the enforcement of the blockade may or may not be appropriate, any comparison to "piracy" is totally wrong. As the widely signed UN Convention on the Law of Sea indicates:

Article101
Definition of piracy
Piracy consists of any of the following acts:
(a) any illegal acts of violence or detention, or any act of depredation, committed for private ends by the crew or the passengers of a private ship or a private aircraft, and directed:

(i) on the high seas, against another ship or aircraft, or against persons or property on board such ship or aircraft;

(ii) against a ship, aircraft, persons or property in a place outside the jurisdiction of any State;

(b) any act of voluntary participation in the operation of a ship or of an aircraft with knowledge of facts making it a pirate ship or aircraft;

(c) any act of inciting or of intentionally facilitating an act described in subparagraph (a) or (b).

No "private ends," no piracy. The rules of blockade are covered by the law of war. See here for a summary.

But you might note that if you attempt to run a known blockade, you are risking trouble.