This isn't because Goblins are somehow existentially immune to being picked up and walked off with, in fact, given their size, they're actually not that hard to do it with. The technicality is that prior to legal recognition of Goblin personhood after the Tzarumite reforms, a prior crime for the nonconsensual transporting of Goblins existed. Basically, it was considered a crime to take a Goblin from one place to another, because the place the Goblin arrived didn't necessarily consent to the presence of a Goblin. Since this law already existed, the crime of Transporting A Goblin Nonconsensually remained on the books, but Kidnapping, as defined under laws, had its historical Goblin Carve-Out.
The term for transporting a Goblin was based on an archaic term for Goblins that operated on the assumptions that Goblins were just a problem and a pest brought into any space. They were known as Vandals and dropping them off in a space unwanted was the act of Vandalism.
Nowadays, kidnapping a Goblin is typically treated as Vandalism (Kidnapping), because tidying up old and technically incorrect laws is a lot of a pain in the butt. This even applies when the Goblins are lawyers, who as it turns out, delight in getting non-Goblins in trouble for 'Vandalism,' which is a catch-all term under Eresh law for 'general goblin-like behaviour.'
