I'd like to thank the original poster of this thread, as he has brought up a great concern; I share a very similar situation, and would like to bring up two situations, though, that I feel need some coverage.
A: As I mentioned earlier, I have a situation similar to that of the OP. The person who initiated the blockade has mentioned that, as soon as all of his wars and aid clear, he will be deleting his nation. This raises a question in my mind, on which I'd like to get feedback: If a nation initiates a blockade, and the controller of that nation later deletes him/herself, can the blockade still stand, without a nation to enforce it?
B: Thanks to five nuclear warheads, and my own stupid neglect to prepare a proper warchest (in my defense, I had just started saving up for National Wonder the Third), I am currently in billtrap. Assuming I can get sufficient resources via external means to clear billtrap, I plan to look into the option of purchasing ships that can counter a blockade. Thus, question the second: If I purchase anti-blockade ships, will they still be able to eliminate a blockade that has been left in place after a war has ended, or do they fail at the attempt?