Blockading Cuba???

Earlier today, Jack posted a brief note on a list of old OLC opinions that have just been compiled and released.  One item just leaped out at me from the list -- this entry:

Authority of the President to Blockade Cuba (January 25, 1961)

Note both the subject and the date.  First the subject:  The social history of the Cuban Missile Crisis is that the idea of a blockade was developed on the spur of the moment as a way of avoiding direct military action.  That is certainly the impression left by histories written by the participants at the time.  But this memorandum makes clear that the idea of a a blockade of Cuba was being mooted for lawfulness more than 18 months before the crisis took place.  Second, the date:  It is just five days after President Kennedy would have been inaugurated, which suggests that this opinion was the product of the Eisenhower administration and finalized, likely, in the rush to conclude work before the transition.  To be sure it was addressed to AG Kennedy, but I take it as almost impossible to have been drafted in the 5 days after the inauguration. I could be completely wrong on this.  My knowledge of the history of the Cuban crisis is limited indeed and perhaps no more than erroneous received wisdom.  But I thought it exceedingly odd to see the idea of a blockade analyzed with some rigor that much before the actual event.  If anyone has any insight into this that explains the timing better, I'd be happy to hear from you.