Nice link there MistressVoluptas, in there in canon source book it lists slavery illegal but in subsection where it's detailed more better what it means, it says any slaves brought to Waterdeep have rights of citizen (so thus you can bring slaves if you from Thay or Calimshan). Slave trading is strictly forbid and any physical assault, maiming or chaining them.<br/><br/>But it does not anyway address what binding demons or devils mean in regards the law and nothing in law forbids it. The law only address any harm caused to city, it's officials or against gods (like make public blasphemy in temple district can get you arrested as public drunken fist brawling with cleric).