Explanation:

- The statement "law as rules of external human action enforced by a political sovereign" was defined by John Austin.

- Austin is famous for his "command theory" of law. He stressed law is a command from a political sovereign, meant to regulate external behaviors, not internal thoughts.

- Holland also wrote on jurisprudence but did not define law exactly in these terms.

- Gray is known for his work on the nature and sources of law, but his definition differs from this.

- Salmond provided a more inclusive definition, focusing on principles recognized and applied by courts.

Correct Answer: Option 1 - Austin