Donald Trump being president is making very clear who is principled and who is just partisan

Rep. Justin Amash, R-Mich., comments about the vote on the defense spending bill and his failed amendment that would have cut funding to the National Security Agency's program that collects the phone records of U.S. citizens and residents, at the Capitol, Wednesday, July 24, 2013. The Amash Amendment narrowly lost, 217-205. The White House and congressional backers of the NSA's electronic surveillance program lobbied against ending the massive collection of phone records from millions of Americans saying it would put the nation at risk from another terrorist attack. (AP Photo/J. Scott Applewhite)

As I write this, Rep. Justin Amash (R-Mich.) is getting into a Twitter war.

Videos by Rare

On Friday, he voted against the waiver proposed for Gen. James Mattis to be secretary of defense. Because Mattis retired from the military fewer than seven years ago, he is legally barred from running the Department of Defense until those years run out.

Most congressional Republicans and a few Democrats were willing to vote in favor of giving Mattis a waiver that would allow him to take the position anyway. His nomination to President-elect Donald Trump’s Cabinet is now a done deal.

RELATED: Republicans and Democrats are already swapping positions on fiscal responsibility

But Amash had other ideas.

As it turns out, the seven-year law doesn’t include any provisions for a waiver. It’s just a prohibition. Here’s the relevant text from the U.S. Code:

There is a Secretary of Defense, who is the head of the Department of Defense, appointed from civilian life by the President, by and with the advice and consent of the Senate. A person may not be appointed as Secretary of Defense within seven years after relief from active duty as a commissioned officer of a regular component of an armed force.

That’s it. You can see it in context, and there’s no mention of a waiver. Congress has made such a waiver just once before (specifically, for Gen. George Marshall in 1950), so there is precedent for the Mattis waiver—but still no legal authority.

This was Amash’s reason for voting no. “It violates the Rule of Law,” he wrote on Twitter in response to a question about his vote. “Laws must apply equally. If Congress doesn’t like a law, then that law should be changed, not waived.”

“Many people incorrectly think the underlying law provides for waivers,” Amash added. (I know I did before seeing his tweets.) “It doesn’t…Congress can waive laws, but such waivers, by definition, violate the Rule of Law.”

As it turns out, Amash was the only Republican who voted no. This has been confusing for some people—and thus the Twitter war.

Because Amash has an R after his name and so does the President-elect, many people undoubtedly assumed he would vote for the waiver along with everyone else. After all, that’s how this works, right? If you’re a Republican in Congress, you’re supposed to vote for what a Republican president wants. If you’re a Democrat, same deal for a Democratic president.

If partisanship is a representative’s guiding value, that makes a lot of sense. But if a member of Congress, like Amash, is voting based not on party but principle—well then it’s crazy talk. What Amash realizes and too many of his colleagues on both sides of the aisle are eager to ignore is the fact that rule of law is so much more important than making life easy for a president who happens to be in the same party as you.

Maintaining (or, at this point, regaining) “a government of laws and not of men,” as Founding Father John Adams famously put it, is a much bigger deal than making sure Donald Trump gets exactly the defense secretary he prefers.

Amash’s vote might be dismissed as nit-picky, and it is certainly true that it is inconsequential in terms of the fate of the Mattis waiver, which easily passed both houses of Congress. But it is emblematic of the sort of winnowing I expect we’ll see in coming days as divisions emerge between politicians who operate out of partisanship and true public servants who are motivated by principle.

(To be clear, when I say “principle,” I don’t simply mean principles I happen to like, such as the rule of law, or elected officials I happen to support, like Amash. Honest principle is always an improvement over shallow partisanship.)

Already we can see this separation occurring on a much larger scale where the Republican budget proposal is concerned. This bill grows the national debt, already sitting disturbingly close to $20 trillion, by a shocking $9 trillion over the next ten years.

RELATED: Obama was right to commute Chelsea Manning’s sentence

Yes, it begins the process of repealing ObamaCare—but $9 trillion! It is Orwellian absurdity for a party that claims the fiscal conservative mantle to even consider a budget like this.

Still, that is exactly what is happening as Republicans, now in power, once again learn to love big government. Amash and the rest of the House Liberty Caucus, along with Sen. Rand Paul (R-Ky.) over in the Senate are among the few dissenters in the GOP.

If present trends are any indication, they can expect a lonely and frustrating next four years in Washington. That is all too often what happens when you choose principle over party.

What do you think?

The hilarious Ellen DeGeneres spoofs “La La Land” with a casting choice we never saw coming

A Good Samaritan saved the life of an Arizona trooper being beaten on the side of a deserted stretch of highway