Spokesperson for the regulatory body Prince Ndamase said on Wednesday this meant the painting was no longer subject to a rating of 16N, which the board introduced in July.
The Goodman Gallery appealed against the classification on September 17, on the grounds that it was "impermissible and unsustainable".
The Spear, painted by Cape Town-based artist Brett Murray, depicted President Jacob Zuma with his genitals exposed.
Ndamase said the FPB would issue a statement outlining its position on the ruling in the next few weeks.
The painting caused outrage, with ruling party supporters marching on the gallery to have the painting removed.
The portrait was also defaced by two members of the public in May.
Barend la Grange (58) and Louis Mabokela (25) are accused of defacing the painting at the gallery by smearing it with red and black paint. – Sapa