It looks like the Kim regime knows a naval blockade would greatly affect them and thus are letting people know early on they will respond militarily if one is implemented:

North Korea lashed out at the United States on Sunday over the possible use of a naval blockade in the wake of its recent missile provocation, warning that it would consider such a move as a “declaration of war.”

The condemnation came after U.S. Secretary of State Rex Tillerson recently mentioned the “right to interdict maritime traffic transporting goods” to and from the North after its Nov. 29 test of an intercontinental ballistic missile capable of striking anywhere on the U.S. mainland.

“We will regard the naval blockade of the United States and its followers as an act of violence against the sacred sovereignty and dignity of the Republic of Korea and as another public declaration of war,” the Rodong Sinmun, North Korea’s ruling communist party newspaper, said in a commentary.

The paper added, “If we see a small movement to put the maritime containment into practice, we must be prepared to follow our immediate and ruthless self-defensive response.”

The Korean Central News Agency, the North’s official newswire service, filed a similar report in English on Friday saying, “The U.S. moves for sea blockade can never be tolerated as they constitute a wanton violation of the sovereignty and dignity of an independent state.”  [Yonhap]

You can read more at the link.