It’s a decision that might change how presidents are elected. Two cases, one filed in Colorado and one by Washington state electoral college members—Chiafalo v. State of Washington and Colorado Department of State v. Baca—will be heard together by the justices. Both states have laws which require electoral college members to vote in line with the popular election results in their state, as do 30 states in the union.

In both cases, the “faithless electors” in question refused to vote for Hillary Clinton even though she’d won the popular vote in both states.

A ruling in Washington State’s Supreme Court in May upheld $1,000 fines given to three electoral college members—Peter Bret Chiafalo, Levi Jennet Guerra and Esther Virginia John—who voted for General Colin L. Powell instead of Clinton during the 2016 election. The ruling declared electors are bound to follow the will of the state’s popular vote, and that the state may regulate the elector’s vote through direct or indirect means.

An August ruling by Colorado’s 10th Circuit Court of Appeals contradicted this verdict; it declared their state’s law unconstitutional. During the 2016 election, one of the state’s electors, Michael Baca, tried to vote for Colorado’s Republican governor, John Kasich, after the state went with Clinton—and had his vote thrown out. Three members who had planned to vote for Kasich with him subsequently changed their vote to Clinton.

Some state officials have expressed concern that such a decision puts all of the power in an election in the hands of a electoral college, removing the import of the popular vote, as exemplified by the Washington State Supreme Court in its brief of the Chiafalo case: “[Such a ruling] would mean that only 538 Americans — members of the Electoral College — have a say in who should be president; everything else is simply advisory.”

The electors in both cases declare that being forced to do so is a violation of their First Amendment rights.

In total, five electors voted against Clinton - two had their votes accepted; three were invalidated and replaced by electors who voted in agreement with the state’s will. The rest cost Clinton votes to Senator Bernie Sanders and Faith Spotted Eagle, a central figure in the Keystone XL Pipeline protests and a Democratic First Nations activist.

President Donald Trump also lost two electoral votes—one to Kasich and one to Representative Ron Paul.

The electoral college is represented by a total of 538 electors. Only 150 electors have gone against the popular vote in casting their ballots throughout the history of the electoral college system, from 1796 to 2016.

A ruling in the case is expected to be returned in June after it is heard by the justices during the spring.

Among other cases, the Court announced Friday that it would also hear appeals related to a 2018 Trump administration ruling easing the way for employers to avoid offering birth control options in healthcare plans via claiming religious or moral exemptions.