why?
Just as a for example, Citizens United, from wiki
In a majority opinion joined by four other justices, Associate Justice
Anthony Kennedy held that the Bipartisan Campaign Reform Act's prohibition of all independent expenditures by corporations and unions violated the First Amendment's protection of free speech. The court overruled
Austin v. Michigan Chamber of Commerce (1990), which had allowed a prohibition on election spending by incorporated entities, as well as a portion of
McConnell v. FEC (2003) that had upheld restricted corporate spending on "electioneering communications". The ruling effectively freed corporations (including incorporated non-profit organizations) to spend money on electioneering communications and to directly advocate for the election or defeat of candidates. In a dissenting opinion, Associate Justice
John Paul Stevens argued that the court's ruling represented "a rejection of the common sense of the American people, who have recognized a need to prevent corporations from undermining self government".
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The Courts use the const and/or BoR to overturn laws fairly commonly.