Reply #4: The restrictions were relaxed by Jimmy Carter for a couple of years:

[Judi Lynn]

The Day the Blockade against Cuba Started

By Mildrey Ponce

January 22, 2007

~snip~
In 1979 the interdiction of U. S. citizens to travel to Cuba was temporally lifted, since President Jimmy Carter did not sign the regulation renewable every six months. The limitation of U.S. dollars Americans could spend in Cuba was also relaxed.

However, the Ronald Reagan administration reinstated the trade “embargo” on April 19, 1982 and the rules for American citizens traveling to Cuba were later modified by the present Cuban Assets Control Regulations.

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http://www.cubanow.net/global/loader.php?&secc=5&c=2&item=1939