Can a property owner be held legally responsible for damage to a neighbors house from a fire set on their property by vagrants? How would one look up the legal code for this?
Who is "their" - the owner or the neighbor? Since you are basically asking whether it is possible, the answer is yes it is possible. There are not "legal codes" that specifically address vagrants setting fires that spread to a neighboring property. If you are one of the parties and it is a real issue, see a lawyer to address all necessary facts.