The Supreme Court has ruled key parts of the 1965 Voting Rights Act as unconstitutional, dealing a disappointing decision to minority voting rights activists and asking Congress to develop new guidelines for the landmark law.

The high court nixed Section 4 of the law, which established a formula for certain states to seek federal approval before making any changes to their voting requirements or laws under Section 5. Those covered jurisdictions had a history of racial discrimination when the law was first passed 5o years ago.

But on Monday, in a 5-4 ruling along ideological lines, the justices deemed that part of the law unconstitutional because the coverage formula is outdated.

“Congress may draft another formula based on current conditions,” Roberts continued in his opinion. “Our country has changed, and while any racial discrimination in voting is too much, Congress must ensure that the legislation it passes to remedy that problem speaks to current conditions.”

However, it is unlikely Congress will pass a new formula, given the political implications of forcing certain states to submit to additional federal requirements. The process would require members to vote to submit their own or other states to a new coverage formula. In particular, Republicans who control the House would loathe submitting their states to a federal mandate.

When Congress reauthorized the Voting Rights Act most recently, they approved it by wide margins and President George W. Bush signed it into law ahead of schedule. But developing a new coverage formula would be a more contentious legislative battle given the controversial issue of voting rights and the political climate on Capitol hill.

The court’s decision does not come as a big surprise to observers, many of whom anticipated this ruling. But the decision will have major implications for state voting laws, especially in the South, for voter ID requirements and redistricting.