Supreme Court Justice Amy Coney Barrett sided with her liberal colleagues on a case involving voting requirements in Arizona - the latest example of her surprisingly moderate approach.

Indeed, Barrett seems to have gradually removed herself from the conservative majority that was solidified under Trump. 

With Barrett on the left, the Supreme Court ruled 5-4 to allow partial enforcement of an Arizona law requiring proof of citizenship to register.

Clarence Thomas, Samuel Alito and Neil Gorsuch would have allowed complete enforcement of the 2022 law, which has never been enforced until now.

Republican win in AZ

In a past dispute involving Arizona, the Supreme Court in 2013 ordered states to "accept and use" the standard federal registration form, which does not require proof of citizenship - only a sworn declaration.

As a result of the ruling, Arizona has a unique system in which over 40,000 voters are "federal only."

In 2022, Arizona passed a new law requiring proof of citizenship to vote for president or by mail, sparking a legal challenge from the Biden administration.

The Supreme Court's latest ruling allows Arizona to reject new voters who lack proof of citizenship and who use a state form to register.

However, the court blocked Arizona from requiring proof from those who fill out the federal form. The court also blocked the law from applying retroactively to the over 40,000 voters who lack proof and who already registered with the federal form.

Arizona is a battleground state that Joe Biden carried by around 10,000 votes in 2020.

"While Democrats have worked to undermine basic election safeguards and make it easier for non-citizens to vote, we have fought tooth and nail to preserve citizenship requirements, see the law enforced, and secure our elections. The Supreme Court has sided with the RNC, and the American people, to protect the vote in November," RNC Chairman Michael Whatley celebrated the decision in a statement.

Barrett sides with libs

The court did not explain its reasoning in a brief order. Barrett sided with the liberals in completely rejecting the appeal from the Republican National Committee.

"Justice Sotomayor, Justice Kagan, Justice Barrett, and Justice Jackson would deny the application in full," the order reads.

Barrett has also broken with conservatives on high-profile cases involving Trump and January 6th.

Earlier this summer, for example, Barrett agreed with the court's liberals that presidential immunity does not prevent "official acts" from being used as evidence in criminal trials.