The song is Laszlo Feyer. The song might be Hungarian trad translated and arranged MacColl - or it might be MacColl pretending that one of his originals is Hungarian trad.

Laszlo Feyer stole a stallion, and is tried and convicted and sentenced to be hanged. His sister (Anna Feyer) learns, and goes with gold and six white horses to buy her brother's freedom. The judge says that only "her sweet favour" will do. While the judge takes her virginity in his golden bed at midnight she hears the gallows groaning, and Laszlo's body is re-hanged in the pine forest to rot.

Then she produces the most magnificent curse on the judge

"Cursed be that judge so cruel
Thirteen years may he lie bleeding
Thirteen doctors cannot cure him
Thirteen shelves of drugs can't cure him".

We are not told of the effect of the curse - but you could always add a verse that did just that (folk process)!