Did Free Blacks Own Slaves?

I had thought that free blacks in Virginia were prohibited from owning slaves by a series of laws passed by the House of Burgesses in the 1680's. The curious (for us) idea of blacks owning blacks is covered in Breen and Innes' Myne Owne Ground, a short monograph on Anthony Hammond, a free black and slaveowner on the Eastern Shore in the mid-seventeenth century. (And just what is so curious about blacks owning blacks? Race never prevented Italians in the 15th century from owning white house-slaves.)

Now here is Jonathan Yardley praising to the skies a new novel, The Known World by Edward P. Jones that chronicles a Virginia county in the antebellum era, that has as its protagonist a black slaveowner. OK, sounds like a fascinating bit of artistry, and I mean to read it...but was it legal?