Not exactly, especially since the “blockade”, is based on Argentina’s claim to sovereignty over the Falkland Islands. Still, depending on where the vessels were “boarded”, (e.g. in the alleged EEZ?), there might be some problem here. In any event, something like economic harassment seems to be going on.
Argentine patrol commanders carrying out interceptions near the South American coast told Spanish captains they were in violation of Argentina’s “legal” blockade of sea channels to the Falklands.
The warning has been backed up in a letter to Aetinape, the Spanish fishing vessels association from the Argentine embassy in Madrid warning boats in the area that “Falklands, South Georgia and the South Sandwich Islands and adjoining maritime spaces are an integral part of the Argentine territory.”
Argentina looks like it is going to do a full court press, both diplomatically and otherwise, to pressure the UK into talks on the Falklands’ future. And I think it has a good chance of working.