Washington (CNN) Sen. Rand Paul is standing by his opposition to the National Security Agency's bulk collection of phone data, saying his position is "about protecting us against systemic bias."

"It's not about the President. It's not about members of my party. It's about the law," the Kentucky Republican said Tuesday night.

His comments came during a brief speech at the Strand Book Store in New York City, where Paul was signing copies of his newly released third book, "Taking a Stand: Moving Beyond Partisan Politics to Unite America."

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He touted his work with Democratic Sen. Ron Wyden of Oregon to block legislation last week extending the NSA's authority, bucking Senate Majority Leader Mitch McConnell, R-Kentucky, and President Barack Obama in doing so.

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