Bit of a difference between a roadblock on the highway and warships boarding a vessel in international waters. Nobody has any right to board a vessel in international waters unless here is a declared state of war between the vessel's respective nations. Any other time it is breach of the law of the sea. Plain & simple! You can all banter about how different situations mitigate breach of the law but it is all self-serving BS from a bunch of hypocrites!.
Not much ... though "Step out of the vehicle, please, Sir" has different implications.
They shoot off their mouths and tell the world their intent (which is to run the blockade) and get called on it. Maybe if they'd just lighten up on the attention-seeking. Breaking through means illegal intent. Would you tell the world if you were running dope through a roadblock?