Not legally, but who cares about legalities with respect to this tiny thorn.
At one time in the not too distant past, Cuban immigration would stamp a little card and place it in the passport where it could be removed by the traveler after their departure. Ergo, no evidence. Prior to that, the official stamp was non-descript and changed frequently, alwasy being placed on pg 7.
I also know people who simply asked that their passport not be stamped, accompanied by a smile and few Yanquis.
Obviously all the above lso requires a little white lie upon re-entry into the US when queried as to what countries one visited.
I'm curious as well as to Marty's experiecne when he was there not too long ago.
I have not kept on this next item in the past couple of years, but even though the law exists (and, by the way, the law does not prohibit travel - merely the spending of money) at that time, no one had ever been prosecuted or successfully fined for trangression.
I personally know of one situation where a traveler was "caught", thank you very much Canadian airline manifests :), and the traveler received a letter from Treasury citing him for illegal travel and a fine of $10k. He asked to have an appeal and the entire thing went away. There was NO procedure in place for hearing an appeal, despite a provision stating one could be requested.