Squids cannot be pulled by leads in the current version of the game. The squid on the lead also cannot be attached to fences. The lead can also stretch on indeffinetly as long as the squid is loaded. It seems as if the squid isn't attatched to a lead at all except for the visual. The squid can however be right clicked to remove the lead. I have tested this on SP MP Gamemode 0 and 1, and on realms with the same results.