They are more like blockades, they just use diplomacy and legal systems instead of parking ships with big guns outside the harbor.

And I suppose the difference between a siege and a blockade is pretty much whether or not you fire those big guns into the city.

I mean, they're really more like trade embargoes, which have existed for hundreds of years. Thomas Jefferson reacted to the Chesapeake affair, for example, by cutting off all international US trade. In retrospect, probably a pretty ineffective foreign policy choice, since it tanked the US economy and didn't particularly hurt the Brits, who were happy that France could no longer trade with the US. (This occurred during the background of the Napoleonic wars and the Royal Navy impressing US sailors).