WATCH: Ben Carson Gets the Constitution Wrong Again

Republican presidential hopeful Ben Carson has shown once again that while he may have been a brilliant surgeon, he's no constitutional scholar.

Interviewed by Chris Wallace this weekend on Fox News Sunday, Carson said it's "an open question" whether the president has to go along with a ruling by the U.S. Supreme Court. Carson has said on several occasions that the president can and should ignore a Supreme Court ruling favoring marriage equality.

Carson tried to say that he said a president can disagree with Supreme Court rulings, and he brought up Abraham Lincoln's reaction to the 1857 Dred Scott decision, in which the court held that African-Americans, enslaved or free, were not citizens, as "a perfect example."

But Wallace pressed him, pointing out that he'd said the president can ignore Supreme Court decisions, even though, since the Marbury v. Madison ruling of 1803, "we have lived under the principle of judicial review, which says if the Supreme Court says this is the law, this is constitutional, the rest -- the executive has to observe that."

"This is an area we need to discuss," Carson responded. "We need to get into a discussion of this because it has changed from the original intent. ... It is an open question."

Constitutional scholars have held that it is not an open question -- and by the way, it took constitutional amendments to abolish slavery and grant black Americans full citizenship (after a bloody Civil War, of course).

Speaking of slavery, Wallace also pressed Carson on his description of Obamacare as slavery and his comparison of the present-day U.S. to Nazi Germany. Watch below; the Supreme Court discussion comes toward the end.