Controversial comedian Dieudonne M'bala was the other witness, despite speaking out against gay marriage.
He was also asked to change out of a white wedding dress. Mr M'bala said: "This is the France of tomorrow."
Italian-born Stranieri, 56, was labelled the 'small ads killer' after targeting victims through classified adverts. He was given a life sentence in 2003 for killing four. Gaiffe, 45, beheaded a man and was given a 30-year sentence in the same year.
The couple met in prison and later made a bizarre claim they had fathered a child with France's then-justice minister Rachida Dati. Miss Dati launched a prosecution for 'causing outrage to a public servant' and the pair had four months added to their sentences.
Prison officials refused to reveal if Stranieri and Gaiffe would now be allowed to share a cell.
Carlos the Jackal, real name Ilich Ramirez Sanchez, is serving two life sentences for bomb plots in Paris in the 1980s and a 1975 double murder.
- DAILY MAIL