Who ended U. S immigrants into Texas?

Law of April 6, 1830 was issued because of the Mier y Terán Report to counter concerns that Mexican Texas, part of the border state of Coahuila y Tejas was in danger of being annexed by the United States. Immigration of United States citizens, some legal, most illegal, had begun to accelerate rapidly. The law specifically banned any additional American colonists from settling in Mexican Territory (which included both California and Texas, along with the areas that would become Arizona, parts of Colorado, Nevada, New Mexico, and Utah.) It also outlawed slavery in Texas.