However, he broke with his party on prominent issues, joining Democrats in filibusters of the USA PATRIOT Act[11] and the Bush administration's 2003 energy bill.
[12] Sununu strongly supported greater access to firearms, voting against the proposed renewal of the 1994 Federal Assault Weapons Ban in 2004.
[14] A long proponent of technology, in January 2007, Sununu called for a permanent ban on taxes of Internet connections and online sales.
[15] Sununu was one of only three senators whose voting record received a score of 100% from the fiscally conservative Club for Growth, in both 2005 and 2006, tying for 1st place.
[18] In 2007, Sununu was the lead Republican co-sponsor of the Clean Air Planning Act of 2007 which sought to address air quality and climate change by establishing a schedule to reduce harmful emissions from power plants—in particular, sulfur dioxide and nitrogen oxides—as well as decrease carbon dioxide emissions through a cap and trade system.
[20] In 2006 Sununu sponsored the bipartisan New England Wilderness Act which added tens of thousand of acres of land to federally protected forests.
The New Hampshire Union Leader praised his decision, citing the Energy Information Agency's estimation that the legislation would cost the American economy $507 billion over 22 years.
He also became well known as one of the five Republican senators who joined Democrats in a filibuster of the USA PATRIOT Act renewal conference report, concerned about possible negative impacts the bill had on civil liberties.
[23] In January 2006, at a hearing in front of the Commerce, Science and Transportation Committee on the Broadcast Flag, Sununu was one of the very few present to criticize the legislation, saying "In all cases [of previous technological advancements in the US], we didn't need to step in with a significant statutory government-regulated mandate on technology that consumers use to enjoy this material".
[24] In October 2006, Sununu voted against a portion of the Military Commissions Act of 2006 that would suspend the right of habeas corpus for non-citizen detainees.
[26] In July 2005, Sununu shaved his head to show solidarity with Senator Arlen Specter, who had lost his hair due to chemotherapy for Hodgkin's disease.
The "Gang of Twenty" bill also lets coastal states participate in decisions and in revenue about drilling in the fifty-to-one-hundred-mile range off their coasts.
To quote the Minneapolis Star Tribune, "Nearly every potentially vulnerable Senate Republican, from Norm Coleman [of Minnesota] to Elizabeth Dole of North Carolina and John Sununu of New Hampshire, has signed on to the legislation.
[29] On July 7, 2010, Akin Gump Strauss Hauer & Feld LLP announced that Sununu was joining the firm as an adjunct senior policy advisor.
[30] Akin Gump is one of the largest law firms and lobbying firms in Washington, D.C.[31] Sununu was appointed by Senate Minority Leader Mitch McConnell to serve on the Congressional Oversight Panel (COP) for the Troubled Asset Relief Program funds, whose purpose is to assess how the TARP program is working, in order to help Congress determine whether to continue injecting capital into the financial sector.
[citation needed] Prior to the 2014 election cycle, speculation had abounded that he would pursue a rematch against Shaheen, but in April 2013, he said that he would not run for his old seat.