Here's a quote from Wikipedia about Plenary Power. It's not quite as simple as @txradioguy @libertybele want it to be and it depends a lot on the judiciary.
"In regard to immigration law, Congress, under the Plenary Power Doctrine, has the power to make immigration policy subject to judicial oversight. The Executive Branch is charged with enforcing the immigration laws passed by Congress. The doctrine is based on the concept that immigration is a question of national sovereignty, relating to a nation's right to define its own borders. Courts generally refrain from interfering in immigration matters.[4] Historically, the U.S. Supreme Court has taken a hands-off approach when asked to review the political branches' immigration decisions and policy-making. The Center for Immigration Studies, an organization with a slant toward isolationism, suggests there is a movement to "erode" political-branch control over immigration in favor of a judge-administered system and that the results have created national security concerns.[4] The U.S. Supreme Court case Zadvydas v. Davis is cited as an example of the U.S. Supreme Court not following plenary power precedent.[4][5]"
I took the part about Plenary power and how it applies to the immigration issue straight from what you just posted. I even just bolded...the relevant part to this discussion for you.
Congress has already passed the law. There are national security implications to enforcing what the Congress...including the Dems against it now...passed 12 years ago.
The Secure Fence Act of 2006 (Pub.L. 109–367) is already singed public law. Divert money from Liberal pork projects to pay for the wall and get it done.
I guess understanding the simplicity of what Trump is authorized to do
really is too hard for you to grasp.
