Which policy did Manuel de Mier y Tehran recommend to the Mexican government

Law of April 6, 1830.

Explanation:

Manuel de Mier y Teran was a Mexican General who issued a report to the government in 1829. In his report, he initialized that slavery should be prohibited and this policy also called to close the borders to forbid any Americans come into the borders of Texas.

He outlined many recommendations in his report, of which many recommendations were adopted into the law under the Law of April 6, 1830. The laws were passed under the Presidentship of Anastasio Bustamante.

Therefore, the correct answer is Law of April 6, 1830.