[colorado tanker]

An interdiction on the high seas is piracy.

So, you think the United States Coast Guard engages in piracy?

[BearCub]

So, you think the United States Coast Guard engages in piracy?

Yes, if it's stopping vessels that aren't either in or entering U.S. waters or waters of nations we have a treaty with. Stopping a vessel on the high seas is piracy.

[Centurion2000]

An interdiction on the high seas is piracy.
So, you think the United States Coast Guard engages in piracy?

If US ships are engaging and boarding ships in international waters, yes they are engaging in piracy.

[BearCub]

Okay, maybe not 'piracy' in that pirates steal and plunder. But boarding ships in international waters raises some questions in my mind.

The Geneva Convention on the High Seas says:

Except where acts of interference derive from powers conferred by treaty, a warship which encounters a foreign merchant ship on the high seas is not justified in boarding her unless there is reasonable ground for suspecting:

(a) That the ship is engaged in piracy; or

(b) That the ship is engaged in the slave trade; or

(c) That though flying a foreign flag or refusing to show its flag, the ship is, in reality, of the same nationality as the warship.

So unless the ship is (a) American, or (b) sailing under the flag of a country with which we have a suitable treaty, our ships can't stop or board.