Senate Democrats on Monday joined a growing number of court cases challenging Matthew Whitaker’s appointment as the acting attorney general on November 7.

Their reason is straightforward: They say Whitaker’s appointment is unconstitutional. The problem: The law is not so clear.

For weeks, legal scholars have debated whether Whitaker — an open critic of special counsel Robert Mueller’s probe into possible Trump-Russia collusion during the 2016 presidential election — could legitimately take up the role.

To put it briefly, those in favor of Whitaker’s appointment say a personnel law allows the president to appoint almost anyone he wants to a top-level position, as long as it’s temporary. Those opposed say the Constitution is clear that the Senate must approve anyone for a short-term top spot.

It’s a heated debate that will now play out in the courts, and possibly force Whitaker out the door along with former Attorney General Jeff Sessions. After he resigned at the president’s request on November 7, the president appointed Whitaker, his chief of staff, to take his place — and there are questions about if he will act independent of Trump’s wishes.

The arguments can be hard to follow, so below is a stripped-down, short guide to the best case each side is making — and why it’s actually quite hard to know who’s right.

The strongest case for Whitaker’s appointment

This argument basically relies on one law: the Federal Vacancies Reform Act of 1998, also known as the VRA.

With that law, Congress authorized the president to appoint someone for 210 days in a federal government role, if the person:

Has worked at the same government agency for at least 90 days preceding the original office holder’s “death, resignation, or beginning of inability to serve”

Receives pay equal or more than what’s known as the GS-15 pay scale, a range that currently goes from $100,000 to $130,000

That’s it, and there’s no question Whitaker meets those requirements. He became Sessions’s chief of staff in October 2017 and was at the GS-15 pay level.

Now, the VRA also made it possible for Trump to appoint Sessions’s “first assistant” — Deputy Attorney General Rod Rosenstein — or someone else serving in a Senate-confirmed position somewhere in the government, but the president didn’t choose either of those options.

Some legal experts say the VRA is vital because it allows the president to keep the government running despite partisan rancor in Congress. “We need the Vacancies Act for temporary gap-filling,” Ann Joseph O’Connell, an expert on government personnel policy at Stanford University, tweeted on November 9. “The modern appointments process is brutal.”

So that seems like a pretty iron-clad case for Whitaker’s appointment, right? Well, maybe.

The strongest case against Whitaker’s appointment

This argument centers around the Appointments Clause in the Constitution. That part — Article II, Section 2, Clause 2 — says that the Senate must “advise and consent” on the naming of any principal officer, even on a “temporary” basis.

A principal officer is someone who reports directly to the president. The attorney general, as an important member of Trump’s Cabinet, does just that. The problem here is that Whitaker is not a Senate-confirmed member of the Trump administration, and therefore has not received the Senate’s green light.

“Senate confirmation exists for a simple, and good, reason. Constitutionally, Matthew Whitaker is a nobody,” lawyers Neal Katyal and George Conway wrote for the New York Times on November 8.

There’s a reason the framers wrote the Constitution that way, these analysts say; they worry a president might appoint loyalists into high-level positions without a check from lawmakers. Certain experts fear Trump chose Whitaker so he would shut down Mueller’s probe, mostly because he once said it had the potential to become a “witch hunt.”

“It would be far better, and more legitimate, to have a Senate-confirmed person in that particular role,” Andy Wright, the founding editor of the Just Security website and former White House lawyer, told me.

So that’s a pretty iron-clad case for Whitaker to not have the job, right? Well, maybe.

See the problem?