President Trump says he can end birthright citizenship with the stroke of a pen, while his critics say that's blatantly unconstitutional, but a a former immigration official says any such move would be resolved at the U.S. Supreme Court and predicting the final verdict is difficult.

At issue is language in the fourteenth amendment to the Constitution, which was drafted following the Civil War to clarify that all constitutional and legal protections must be afforded to former slaves just as with every other American.

"All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the state wherein they reside. No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any state deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws," reads the first section of the amendment.

Temple University School of Law Prof. Jan C. Ting served as assistant commissioner of the Immigration and Naturalization Service at the Justice Department from 1990-1993.  He says people need to understand there are long-established exceptions to the first line of the amendment.

"It's a gross overstatement, that we hear all the time, that the fourteenth amendment means every single person born in the United States is automatically a citizen," said Ting, pointing out that children of ambassadors or conquering soldiers do not qualify as citizens if they are born here.

He also noted that anyone still pledging loyalty to a sovereign outside of the United States can be blocked from citizenship if they are born here.  The Supreme Court made a such a ruling against American Indians in Elk v. Watkins.

According to Ting, the phrase "subject to the jurisdiction thereof" is what leads to fierce debate, since federal and state authorities can clarify the laws in their jurisdictions.

But can Trump clarify the law on his own or does Congress need to act?  If Trump issues such an order, Ting says any challenge would immediately enter the court system and eventually wind its way to the Supreme Court.

Listen to the full podcast as Ting explains why the powers of the president on immigration policy are very broad and why President Obama's controversial immigration orders will also be decided by the courts.