In 1959, he became a member of the fledgling Orleans Parish Republican Executive Committee. He also headed the New Orleans Young Republicans Club and worked in the 1960 campaign for Richard Nixon in Louisiana, but the state handily cast its electoral votes for John F. Kennedy. He worked in the Barry M. Goldwater campaign in 1964, when Goldwater became only the second Republican since Reconstruction to carry Louisiana. Feldman was a Louisiana delegate to the 1968 and the 1972 Republican National Conventions, both of which met in Miami Beach, Florida, to nominate the Nixon-Agnew tickets, which in the second campaign won in forty-nine states. Feldman was among seventy-one Jewish delegates and alternates to the convention. In 1974, Feldman lost a race, 67–32, in the Republican State Central Committee to John H. Cade, Jr., for selection as Louisiana Republican National Committeeman.
On September 3, 2014, Feldman issued a ruling upholding Louisiana's ban of same-sex marriage. After the United States Supreme Court ruled Section 3 of the Defense of Marriage Act, the federal statute that banned the United States federal government from recognizing same-sex marriage, as unconstitutional in United States v. Windsor, he was the only district federal judge to uphold a state prohibition against same-sex marriage. Feldman said that the state has a legitimate interest in upholding the state's 2004 amendment to the state constitution defining marriage as between one man and one woman that was approved by 78% of voters. Feldman stated, "marriage is a legitimate concern of state law and policy, and that it may be rightly regulated because of what for centuries has been its role." Feldman also equated the recognition of marriage without regard to sex to incest, writing that he was concerned that recognizing marriage without regard to the sex of the members of the couple would lead to a slippery slope that would eventually require courts to recognize polygamy and incest. Lawyers for the plaintiffs immediately announced plans to appeal the ruling. In January 2015, the case was heard in the Fifth Circuit Appeals Court, alongside cases from Texas and Mississippi. The decision remained unresolved at the time of the June 26th Obergefell decision. Following the Supreme Court decision, the appeals court remanded the case back down to Feldman and the district court for a reversal of order ruling in favor of the Louisiana plaintiffs.
On June 22, 2010, Feldman issued a preliminary injunction blocking a six-month moratorium on deep-water offshore drilling in Hornbeck Offshore Services LLC v. Salazar. White House press secretaryRobert Gibbs indicated that the Obama administration intended to immediately appeal the decision to the Fifth Circuit Court of Appeals. Feldman's 2008 financial disclosure report indicates that in that year, he owned stock in Transocean, the company that owned the Deepwater Horizon rig, as well as in other oil companies which would be affected by the moratorium. A federal judge is required to consider recusal when he owns shares in one of the parties in the case before him, however none of the companies listed in Feldman's 2008 disclosure were directly involved in the action against Salazar. Feldman's 2009 financial disclosure report indicates that he had financial investments in multiple BlackRock funds, each valued under $15000, much like the prior year. Although Blackrock was said to be the largest holder of BP stock, it's not clear that any of these funds held stock in BP. Feldman held stock in Exxon-Mobil during the hearing on the drilling moratorium and from June 8 to June 21, he issued several orders related to the moratorium case. On June 22, at the "opening of the stock market", he reportedly sold his Exxon-Mobil stock. Hours later, he issued his ruling lifting the moratorium. As of the June 9, 2010 amended complaint, Transocean, Black Rock, BP, and Exxon-Mobil were not plaintiffs in the action.
