Many wondered why Mr Obama's letter was still being used after all this time since it seems like such a simple fix. No official response has come from the White House on the matter as yet. However, Mr Trump has been known for his anti-immigrant rhetoric. He is still championing a nearly 2,000-mile border wall with Mexico to limit illegal immigration and has not explained why he repeatedly says Mexico will pay for it. His latest iteration is the travel ban, restricting those from six Muslim-majority countries from entering the US.