How did Citizens United v. Federal Election Commission affect campaign-finance laws in the United States?

The 2010 Supreme Court ruling in Citizens United v. Federal Election Commission significantly altered U.S. campaign-finance law by invalidating key restrictions on political spending.12

The Court ruled (5–4) that laws prohibiting corporations and unions from using general treasury funds for independent "electioneering communications" violated the First Amendment guarantee of freedom of speech. This decision struck down Section 203 of the Bipartisan Campaign Reform Act (BCRA) of 2002 and overturned portions of previous rulings, including McConnell v. Federal Election Commission.12

By declaring that independent expenditures could not be constitutionally limited, the ruling paved the way for the creation of super PACs. These organizations are permitted to raise and spend unlimited sums from corporations, unions, and individuals to support or oppose candidates, provided the expenditures are made independently and not in coordination with the candidates themselves. Critics, including then-President Barack Obama, argued the decision would allow special interests to spend without limit in elections, while supporters viewed it as a victory for free speech.31