The U.S. Supreme Court has struck down a key pillar of campaign finance law and expanded how much political donors can give candidates, in a move critics said would hand further power to special interests and the "super rich."

In a landmark 5–4 vote Wednesday, the court voided the overall limits under federal law limiting the total that individuals can give to candidates, parties and political action committees during the federal two-year election cycle.

The ruling means that Americans have a right to give the legal maximum to candidates for Congress and president, as well as to parties and PACs, without worrying that they will violate the law when they bump up against a limit on all contributions, set at $123,200 for 2013 and 2014. That includes a separate $48,600 cap on contributions to candidates.

But their decision does not undermine limits on individual contributions to candidates for president or Congress, now $2,600 an election. The ruling also leaves in place laws that require candidates, parties and political action committees to disclose information about donors.

Nonetheless, the decision was quickly attacked by advocates of government transparency.

"Once again, the Supreme Court has given more power to special interests and a tiny percentage of the very rich," The Sunlight Foundation said in a statement.

The court was divided over how sweeping the ruling actually is. The biggest impact is that a single donor can now give the maximum amount by law to as many federal candidates, parties and committees as he or she wishes.

The 5–4 split was along party lines, with the five justices appointed by Republican presidents joining the majority and the four appointed by Democratic presidents dissenting.

"I am concerned that today's ruling may represent the latest step in an effort by a majority of the Court to dismantle entirely the longstanding structure of campaign finance law erected to limit the undue influence of special interests on American politics," said Sen. John McCain, R-Ariz., in a statement released following the decision.

McCain said there would be "scandals involving corrupt public officials and unlimited, anonymous campaign contributions" that would force another reform in the future.

Chief Justice John Roberts, writing on behalf of the court, said the justices did not reach the question of whether to overturn a key 1976 ruling, Buckley v. Valeo, which upheld limits on campaign finance donations while also describing how courts should analyze such regulations.

Justice Clarence Thomas, who voted with Roberts, said the court had gone further than the chief justice claimed. Roberts said in his opinion that the aggregate limits violated the First Amendment of the U.S. Constitution, which protects free speech.

But not everyone saw it that way.

"What this court fails to recognize is the First Amendment rights of the 99.9% of citizens who cannot buy access to elected officials in order to give voice to their issues," the Sunlight Foundation said. "Seven-figure contributions are not a megaphone merely amplifying the voices of the donors, they are a sonic boom, overpowering to the point of silencing all other voices."

He rejected the contention of President Barack Obama's administration that the limits are needed to fight corruption. The caps "do little, if anything, to address that concern, while seriously restricting participation in the democratic process," wrote Roberts, appointed by former President George W. Bush.

The decision comes four years after the court's landmark Citizens United v. Federal Election Commission ruling, which cleared the way for increased independent corporate and union spending during federal elections.

In a dissenting opinion, Justice Stephen Breyer said the ruling, along with Citizens United, "eviscerates our nation's campaign finance laws." Wednesday's ruling could threaten the legal architecture that underpins other campaign finance regulations.

The aggregate limits have been in place, in various forms, since 1974, with the most recent version dating back to the 2002 Bipartisan Campaign Reform Act.

Republican donor Shaun McCutcheon, an Alabama businessman, and the Republican National Committee had challenged the contribution caps. Before Wednesday's Supreme Court decision, donors could not exceed the $123,200 overall limit during the two-year period. The case is McCutcheon v. Federal Election Commission, U.S. Supreme Court, 12-536.

Al Jazeera and Reuters