Question: Were United States v. Nixon and Zelman v. Simmons-Harris both US Supreme Court cases?

<P0-S0> Stephen P. Halbrook is a Senior Fellow at the Independent Institute and an author and lawyer known for his litigation on behalf of the National Rifle Association. <P0-S1>  He has written extensively about the original meanings of the Second Amendment and the Fourteenth Amendment (the latter as applied to Second Amendment rights). <P0-S2>  He has argued and won three cases before the US Supreme Court: "Printz v. United States", "United States v. Thompson-Center Arms Company", and "Castillo v. United States". <P0-S3>  He has also written briefs in many other cases, including the Supreme Court cases "Small v. United States" (pertaining to the Gun Control Act of 1968) and "McDonald v. Chicago". <P0-S4>  In "District of Columbia v. Heller", he wrote a brief on behalf of the majority of both houses of Congress. <P0-S5>  More broadly, his decades of research on the Second Amendment contributed to the intellectual foundation of the "Heller" decision. <P0-S6>  He has written many books and articles on the topic of gun control, some of which have been cited in Supreme Court opinions ("Heller", "McDonald", "Printz v. United States"). <P0-S7>  He has testified before congress on multiple occasions. <P0-S8>  Halbrook’s most important scholarly contribution, however, was the book "That Every Man Be Armed", originally published in 1986. <P0-S9>  The book was the most thorough analysis of the legal history and original intent of the Second Amendment. <SEP> <P1-S0> United States v. Nixon, 418 U.S. 683 (1974), was a landmark United States Supreme Court decision which resulted in a unanimous 8–0 ruling against President Richard Nixon, ordering him to deliver presidential tape recordings and other subpoenaed materials to the District Court. <P1-S1>  Issued on July 24, 1974, the ruling was important to the late stages of the Watergate scandal, when there was an ongoing impeachment process against Richard Nixon. <P1-S2>  "United States v. Nixon" is considered a crucial precedent limiting the power of any U.S. president to claim executive privilege. <SEP> <P2-S0> Hollingsworth v. Perry refers to a series of United States federal court cases that legalized same-sex marriage in the State of California. <P2-S1>  The case began in 2009 in the U.S. District Court for the Northern District of California, which found that banning same-sex marriage violates equal protection under the law. <P2-S2>  This decision overturned ballot initiative Proposition 8, which had banned same-sex marriage. <P2-S3>  After the State of California refused to defend Proposition 8, the official sponsors of Proposition 8 intervened and appealed to the Supreme Court. <P2-S4>  The case was litigated during the governorships of both Arnold Schwarzenegger and Jerry Brown, and was thus known as Perry v. Schwarzenegger and Perry v. Brown, respectively. <P2-S5>  As "Hollingsworth v. Perry", it eventually reached the United States Supreme Court, which held that, in line with prior precedent, the official sponsors of a ballot initiative measure did not have Article III standing to appeal an adverse federal court ruling when the state refused to do so. <SEP> <P3-S0>  The Court decided that the program did not violate the Establishment Clause of the First Amendment even if the vouchers could be used for private, religious schools. <P3-S1> Zelman v. Simmons-Harris, 536 U.S. 639 (2002) , was a 5-4 decision of the United States Supreme Court that upheld an Ohio program that used school vouchers.