The Supreme Court on Thursday blocked the Trump administration from adding a question about citizenship to the 2020 census for now, and asked the Commerce Department to offer a better explanation for why it made the move.

The opinion pointed to questions raised by civil rights groups and Democratic-led states, which argued that the reason Commerce Secretary Wilbur Ross gave was a pretext that would actually skew the count in a way that would help Republicans.

[It’s not just the citizenship question. 2020 census faces other woes]

Ross has contended that he added the question to help the Justice Department enforce a voting rights law. The challengers say the question would count up to 9 million few people in immigrant communities, where households with noncitizens will be less likely to respond.

Chief Justice John G. Roberts Jr., who joined the liberal wing of the court for the majority, wrote that the voting rights enforcement rationale — the sole stated reason — “seems to have been contrived” and was “more of a distraction.”