In mid-March, President Donald Trump invoked an almost-never-used federal law, claiming that it gives him the power to deport many immigrants at will with minimal or no legal process to determine if these deportations are lawful. The text of that statute, the Alien Enemies Act of 1798, does not give presidents the power Trump claims.

For the moment, at least, a lower court order blocks Trump’s Alien Enemies Act proclamation; that order is still in effect, although there is ongoing litigation about whether the Trump administration defied it by sending dozens of Venezuelan immigrants to a prison in El Salvador after the lower court ordered the planes carrying these immigrants to be turned around.

Now Trump wants the Supreme Court to halt the lower court order and effectively allow him to resume deportations without any meaningful review, and without having to prove the immigrants targeted by his proclamation have actually done anything wrong. The case, which is known as Trump v. J.G.G., is before the Court on its “shadow docket,” a mix of emergency motions and other matters which the justices often decide after only cursory review of the case. A decision on the case could come any time in the next few weeks.

In J.G.G., Trump’s lawyers make three arguments that, when combined, would give him virtually unchecked authority to remove any noncitizen from the United States.

First, Trump claims the unprecedented authority to invoke the Alien Enemies Act during peacetime, and against a nonstate actor — in this case, Tren de Aragua, a criminal gang that originated in Venezuela. That law, which does give the president sweeping authority to remove foreign nationals when properly invoked, only applies during a “declared war between the United States and any foreign nation or government,” or during a military “invasion or predatory incursion” of the United States.

Congress — the only branch of government that can declare war — has not declared war on Venezuela, and the alleged presence of civilian criminals........

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