“What is our country coming to,” President Donald J. Trump Tweeted this weekend, “when a judge can halt a Homeland Security travel ban and anyone, even with bad intentions, can come into U.S.?”

Trump’s question highlighted a central tenet of how the US government operates: only the court system has the authority to decide whether a law enacted by the president or Congress is legal.

And this weekend, a federal judge said Trump’s ban did not clearly enough fall into the “legal” category to continue operating. Trump took to Twitter to criticize the decision — and the court system — but the White House can do little else except accept the court’s authority.

I have instructed Homeland Security to check people coming into our country VERY CAREFULLY. The courts are making the job very difficult!

— Donald J. Trump (@realDonaldTrump) February 5, 2017

So how does the court system decide whether the ban is legal? Here’s a rundown of what we can expect in this round of Trump vs. the judicial system.

A Temporary Stop to the Ban

- On Friday, one week after the ban took effect, a federal judge in Seattle temporarily halted it from being carried out by border agents until the court could hear arguments from both sides and sort out whether it was constitutional.

- The temporary stop is called an “injunction” and when a federal court issues a nationwide injunction, the whole country must comply, even if other courts disagree. A federal court in Boston did, in fact, disagree, but the Seattle injunction stands anyway.

- The judge, James Robert of the Western District of Washington federal court, was appointed by President George W. Bush, a Republican. He said there was “no support” for Trump’s argument that the law was needed to protect the US from individuals from the banned countries.

- The state of Washington was the one that brought the case against the federal government, and Washington Attorney General Bob Ferguson said he hopes “the federal government will understand what they did was unconstitutional and unlawful.”

The White House Doubles Down on the Ban

- The White House, in response, called the court’s decision “outrageous” and the Department of Justice appealed the judge’s decision, asking a federal appeals court to lift the injunction and allow border patrols to once again enforce the ban.

- The US Court of Appeals for the 9th Circuit declined taking immediate action, but asked both sides to file their arguments by this afternoon.

- Washington, Minnesota, and Hawaii filed arguments against the ban, along with a slew of former senior foreign policy officials and technology companies.

- The Justice Department has to file its argument by 3 p.m. PST.

- The Appeals court could keep the injunction in place or lift it by issuing a “stay.”  Either way, the case will continue to be litigated in courts across the country.  

The Legal Arguments

- Washington and Minnesota both said the ban harmed their economies, with Washington citing 76 Microsoft employees who are citizens of the banned countries and Minnesota saying affect 80 individuals at the Mayo Clinic.

- The states challenging the ban argue that it is unconstitutional, discriminatory, targets individuals based their country of origin or religion without justification, does away with due process, and was designed to harm a particular group.

- The lawyers defending the ban say the president has the authority to enact the ban, and say the states don’t have the authority to challenge it — another legal question for a judge to decide.

- Former Secretaries of State Madeleine Albright and John Kerry and former CIA Director Michael Hayden signed a declaration in support of Washington and Minnesota’s case against the president’s executive order, which Trump signed Jan. 27.

The Future of the Ban

- The ban could be reinstated as early as today, but the side that loses could then ask the Supreme Court to intervene. The Supreme Court could choose to take up the case or leave the Appeals’ court decision in place.

- There are multiple legal challenges in courts across the country to Trump’s ban. Each of those cases will take weeks, months, or even years to sort out. The ban could be reinstated, halted again, and lifted again throughout that process, and wind up going to the Supreme Court again.

- If the Supreme Court takes up the question of whether the ban is legal, it will affect all of the other cases. The case’s outcome, at that point, will likely be influenced by whether or not Trump’s nominee to the Supreme Court, Neil Gorsuch, is confirmed and sitting on the bench.

- The ban, although “temporary,” may linger in the US court system for a long time.