That doesn't mean it should be difficult to arrest, wiretap, or detain suspected al-Qaeda members, warrants should be particularly easy to get since September 11th. And non-citizens have no constitutional right to stay here, just rights while they ARE here; if here illegally, they can be deported or detained without violating their constitutional rights!
So essentially, they have no liberty that can not be easily taken away, thus their LIBERTY (an "unalienable" right) is NOT protected from the States by the 14th Amendment, nor from the US Government by the 5th Amendment.
I believe this contradicts what Barr said. Maybe Barr didn't really say anything that meant anything, when you get right down to it. Just a posturing moment for another politician.