What is birthright citizenship? It derives from the Fourteenth Amendment to the US Constitution, ratified in 1868. This was three years after the Civil War had ended, and followed the Thirteenth Amendment, which ended slavery. The purpose of the Fourteenth amendment was to prevent the newly-reconstituted governments of the defeated Confederacy from denying citizenship to the Freedmen, the liberated slaves. The amendment referred specifically to "those born under the jurisdiction of the United States," and by that meant those former slaves born in the US. The amendment, and laws such as the 1870 Naturalization Act and others, clearly did not grant citizenship to anyone else - such as those who illegally crossed our borders. The path to citizenship was clearly laid out in those subsequent laws, and in no way were those laws intended to convey citizenship to babies whose mothers had illegally crossed our borders. To repeat: the amendment was to give citizenship to former slaves, and not to anyone else.
However, in the past few decades, the US government has reinterpreted the amendment to mean "if you were born in America, you are a citizen," even if you are under the jurisdiction of another country. The key phrase is "under the jurisdiction," which originally meant "born in the US but not a citizen of any other country." This applied to the former slaves, but not to tourists, diplomats, etc. and certainly not to illegal aliens. The modern, "progressive" interpretation applies it to everyone, even those who parents are citizens of another country who are here illegally.
Conservatives for a long time have been objecting to the application of birthright citizenship to the children of non-citizens, and think that the President is correct to try to bring the practice to a halt. President Obama repeatedly said he did not have the power to grant residency to the minor children of illegal immigrants. He said this right up to the point that he approved his DACA measure by executive order, despite his own protestations and despite Congress's refusal to pass it. The legal ground under President Trump on birthright citizenship may be shaky, but no more so than that under President Obama.
The United States is a magnet for those seeking liberty and freedom, but we also are a place where the rule of law matters. We have established processes for immigration and for naturalization of citizens, and it is absurd to contend that the executive,the legislative and the judicial branches of our government place so little value on the rights and responsibilities of citizenship that they would intend them to apply not merely to legal citizens, legal residents,and legal immigrants,but to everyone in the world who manages to evade the authorities and set foot in America. The United Kingdom and Germany ended "birthright citizenship" decades ago, when faced with a growing tide of illegal immigration. Most places today do not grant citizenship to illegal immigrants nor to their children, and the United States should not either. We as a nation will welcome those from anywhere who come here legally and aspire to be Americans, but it is a completely different thing indeed to incorporate those who come here illegally. Citizenship is the ultimate prize, and if we pass it out as if it were some type of "participation trophy" instead of something to be earned, its value is diminished. We emphasize, the process by which one becomes a naturalized US citizen may be challenging, but millions and millions of Americans have accomplished it. They met the standards and passed the qualifications. Why should the same reward be granted to illegal immigrants, and by what standard can any citizen of any other country demand to be admitted here?