The only thing standing between U.S. Attorney General Jeff Sessions and the medical marijuana patients and providers that he seems to want to send to prison is an obscure provision of federal funding law. But that could all change this week.

Under current federal law, the U.S. Department of Justice and component agencies like the Drug Enforcement Administration (DEA) are barred from spending money to interfere with the implementation of state medical cannabis laws. That’s due to a bipartisan rider — known as the Rohrabacher-Farr amendment, after its chief sponsors — that has been approved by Congress and attached to federal appropriations bills for the past two fiscal years.

But funding for the federal government — along with policy amendments like the cannabis one — is currently set to expire on Friday, unless Congress acts.

Due to brinksmanship and battles over funding for healthcare and President Trump’s proposed Mexican border wall, there’s a real chance that lawmakers won’t reach a deal in time to avert a government shutdown.

But under a shutdown scenario, it’s not as if the entire federal government comes to a halt. So-called “essential” or “excepted” services would continue uninterrupted.

And federal law enforcement agencies like the Drug Enforcement Administration (DEA) are considered essential, the feelings of marijuana legalization advocates aside.

“All agents in DEA field organizations are excepted from furlough because they support active counternarcotics investigations,” a recent Justice Department shutdown contingency plan states. “DEA investigations need to continue uninterrupted so that cases are not compromised and the health and safety of the American public is not placed at risk.”

Policy riders like the medical cannabis protections, on the other hand, are not considered essential.

That means that if Congress fails to pass a new spending bill by Friday, Attorney General Jeff Sessions could be overseeing DEA raids on medical marijuana businesses that are legal under state law as soon as this weekend.

The current dispute concerns funding for current Fiscal Year 2017, and advocates expect that the medical cannabis protections and most or all other current policy riders will be included in an extension through September 30 — if and when lawmakers reach a broader deal on federal spending.

It is also possible that lawmakers will pass a shorter-term extension to buy themselves more time to work out deals for funding the border wall and other matters, and it is likely that the marijuana provisions would be extended as part of that temporary fix as well.

A Yearly Cannabis Funding Fight

Because the medical cannabis protections only cover annual appropriations bills, they must be reconsidered every year, and supportive members of Congress are already fighting hard to get the language included in Fiscal Year 2018 legislation as well.

If the medical cannabis protections aren’t included in the initial version of the FY18 legislation that Republican leaders will introduce in the next few weeks, supporters will have to fight to add it via an amendment, most likely on the House floor and/or in the Senate Appropriations Committee.

In 2014 the measure was approved in the House by a vote of 219-189, and support grew in 2015 to 242-186. The measure was also approved twice by the Senate spending panel with similarly strong margins, and the language was included in the final spending packages signed into law by then-President Obama.

Since then, the federal government has been operating on temporary funding extensions without having individual appropriations bills brought forth under regular order.

Since the last House floor vote several more states have enacted medical cannabis laws or ended marijuana prohibition altogether, and a number of legalization opponents who consistently opposed the measure in the past have retired and been replaced with freshman supporters.

As a result, reformers are confident that if the amendment comes to a vote in the House, they have more than enough support to pass it again.

But that’s if there is a vote on the amendment this year. They have reason to be concerned, because in 2016 House leadership begin restricting the scope of policy riders that were allowed to come to the floor in accordance with the rules under which spending bills are considered. Last summer, for example, proposed amendments on banking services for marijuana businesses and Washington, D.C.’s ability to spend its own money regulating cannabis were blocked from even being considered on the House floor.

So while legalization advocates are optimistic that they have the votes to pass the state medical marijuana protections again and extend them through most of 2018, it’s an open question as to whether they will even get the opportunity.

Trump Administration’s Cannabis Calculus

Even if the government shuts down and Sessions and the DEA technically regain the ability to enforce federal prohibition laws against state-legal medical cannabis patients and businesses this weekend, it doesn’t necessarily mean they will do so.

As a candidate on the campaign trail, President Trump repeatedly pledged to respect state marijuana laws. Perhaps more importantly, he also specifically said he personally supports medical cannabis “100 percent” and knows people who have benefited from it. A reversal, particularly against medical marijuana — which polls now show is supported by 94 percent of Americans — has the potential to be a political disaster and a huge distraction from the rest of the administration’s agenda.

And since inauguration day, White House Press Secretary Sean Spicer has suggested on a number of occasions that Trump understands the value of medical cannabis, even going so far as to specifically reference the appropriations rider that protects people following state laws.

In the next few weeks, President Trump will release his first full budget request to Congress, and he will have to decide whether to propose that lawmakers delete the existing medical cannabis protections or continue them into the next fiscal year.

Wheres President Obama’s administration in its second term took a generally hands-off approach to state marijuana laws, his last two budget requests actually specifically suggested deleting the medical marijuana provisions.

For now, the cannabis industry and the patients it serves are watching to see whether the federal government shuts down and the protections they’ve been relying on for the past two years will disappear this week and, if so, for how long.