(WASHINGTON) — The United States Supreme Court on Friday, by a vote of 6-3, said an effort to block President Donald Trump from excluding undocumented immigrants from a key Census count was “premature,” effectively allowing the administration to move forward with its plans even as the justices left the door open to future challenges.

By subtracting millions of immigrants from the Census total, Trump hopes to shape the apportionment of congressional seats, the allocation of billions in federal funds and the contours of the nation’s electoral map for at least the next decade. If he succeeds, it would be the first time in 230 years that the process would exclude large swaths of people inside the U.S.

The Court’s conservative majority, in an unsigned opinion, said the scope and impact of the president’s promised action is not yet clear.

“At present, this case is riddled with contingencies and speculation that impede judicial review,” the Court said.

“The President, to be sure, has made clear his desire to exclude aliens without lawful status from the apportionment base. But the President qualified his directive by providing that the Secretary should gather information ‘to the extent practicable’ and that aliens should be excluded ‘to the extent feasible.’ Any prediction how the Executive Branch might eventually implement this general statement of policy is no more than conjecture at this time,” it said.

While the Census concluded earlier this year, the government told the Court last month that analysts at the Commerce Department, which oversees the U.S. Census Bureau, were still trying to estimate the number of undocumented immigrants in the country, including a breakdown of long-term residents and more recent arrivals.

“The count here is complete; the present dispute involves the apportionment process, which remains at a preliminary stage,” the Court’s majority said. “The Government’s eventual action will reflect both legal and practical constraints, making any prediction about future injury just that — a prediction.”

In dismissing the challenge to Trump’s plan for now, the Court made clear that it was not a decision on the merits. “We hold only that they are not suitable for adjudication at this time,” they said.

Justice Stephen Breyer, in a dissenting opinion joined by Justices Sonia Sotomayor and Elena Kagan, said they would have decided the case and ruled against Trump.

“The Constitution specifies that the number of Representatives afforded to each State is based on an apportionment of the total population, with each State receiving its proportional share. The Government has announced a policy to exclude aliens without lawful status from the apportionment base for the decennial Census. The Government does not deny that, if carried out, the policy will harm the plaintiffs. Nor does it deny that it will implement that policy imminently,” Breyer wrote.

“The plain meaning of the governing statutes, decades of historical practice, and uniform interpretations from all three branches of Government demonstrate that aliens without lawful status cannot be excluded from the decennial Census solely on account of that status. The Government’s effort to remove them from the apportionment base is unlawful, and I believe this Court should say so,” he wrote.

Immigrant advocates who sued Trump over the policy stressed that the Court’s move does not mean the fight is over.

“This ruling does not authorize President Trump’s goal of excluding undocumented immigrants from the Census count used to apportion the House of Representatives,” said ACLU attorney Dale Ho. “The legal mandate is clear — every single person counts in the Census, and every single person is represented in Congress. If this policy is ever actually implemented, we’ll be right back in court challenging it.”

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