WASHINGTON — Voter rights were back on the agenda at the Supreme Court as the nation’s top court took up a controversial law that requires stringent proof of citizenship for voter registration.

At issue is an Arizona law that aims to block illegal immigrants from casting ballots by demanding proof well beyond what is required under federal law of those seeking to inscribe their names on voter lists.

The latest legal bout comes just weeks after the Supreme Court heard arguments over — and appeared poised to overturn, at least in part — the 1965 Voting Rights Act, which requires nine mainly southern states and local governments in seven other states to obtain Justice Department approval for any changes in their electoral codes.

Arizona, in the US southwest on the border with Mexico, has butted heads with Washington several times over its immigration initiatives. But four other states, including Alabama, Georgia, Kansas and Tennessee — have enacted similar laws, and 12 more states are working on doing the same.

The nine Supreme Court judges seemed split on the issue, with some saying the signed affidavit on the form was sufficient, while others suggesting the extra proof from official documents was preferable.

Ultra-conservative judge Antonin Scalia was among the latter group, saying that “a statement under oath is not a proof at all.”

The conservative justice Samuel Alito also chimed in to disparage what he called a “crazy system.”

But the federal government, in a brief filed in favor of striking down the Arizona law, argued that it sets a dangerous precedent.

If Arizona is allowed to require documents proving citizenship beyond what is required at a national level, “each state could impose all manner of its own supplemental requirements beyond the federal form,” the government said.

Analyst Doug Kendall, president of the Constitutional Accountability Center, said a majority of the Court “appeared to recognize that the entire point of having a single Federal form was to streamline the voter registration process.

“Approving Arizona’s law would pave the way for a patchwork of 50 state forms,” he said.