28 U.S. Code § 1870 – Challenges

In civil cases, each party shall be entitled to three peremptory challenges. Several defendants or several plaintiffs may be considered as a single party for the purposes of making challenges, or the court may allow additional peremptory challenges and permit them to be exercised separately or jointly.
All challenges for cause or favor, whether to the array or panel or to individual jurors, shall be determined by the court.