This morning, Attorney General Jeff Sessions announced changes to Obama-era marijuana policy guidelines that had in effect allowed several states to move forward with pot legalization even though it remains illegal under federal law. Sen. Cory Gardner, a Republican from Colorado, one of the legalizing states that has benefited from Obama’s approach, immediately objected.

And in doing so, he reminded the world of what so many people in Washington seem to have forgotten in the era of Trump: United States senators have actual powers of office that they can (and frequently do) use to try to get their way on issues that are important to them.

I am prepared to take all steps necessary, including holding DOJ nominees, until the Attorney General lives up to the commitment he made to me prior to his confirmation. — Cory Gardner (@SenCoryGardner) January 4, 2018

I’m not sure if Gardner’s gambit here will work or not — that will depend on what level of support he gets from other senators — but it certainly might work.

And in doing so, it debunks the often-heard theory that senators like John McCain, Jeff Flake, Bob Corker, and Susan Collins, who have expressed serious doubt about Donald Trump, can’t be blamed for consistently voting with him on nominees and legislation. It’s true that the reason Trump has secured near-unanimous GOP support for all his nominees is that he has hewed closely to conservative orthodoxy. But US senators have never been bound by that kind of policy literalism.

When Gardner threatens to hold up DOJ nominations, he’s not saying he will hold up nominees who disagree with him about marijuana policy. He’s saying he will hold up everyone regardless of the merits, in order to try to get his way on marijuana policy.

That’s standard-issue behavior for a US senator. And by the same token, if Flake or Corker or anyone else wants to shift Trump’s behavior on any topic, this is the way to do it. You don’t need to wake up one morning and become a liberal. But you also don’t need to write a book or give a speech or deliver a grandstanding interview. What you need to do is use your concrete powers of office to hold up things that other people care about until you get your way on an issue that you care about.

Republicans could, if they wanted to, demand that Trump stop mixing his business interests with politics. Or stop employing his unqualified son-in-law as a top White House aide. Or stop lying relentlessly about election fraud. Or whatever of a dozen other things he does that aren’t related to the main elements of conservative ideology. But they keep choosing on a daily basis not to do so, engaging in a form of “ideological collusion” that threatens the stability of American institutions.

Gardner’s actions today are a reminder that the GOP legislative caucus hasn’t forgotten how to use its powers of office — it’s simply decided not to.