Pot smokers in Washington, DC, are about to face a dizzying predicament. Come Thursday, residents of the US capital will be able to legally possess two ounces of marijuana and grow up to six plants. They can also trade or gift up to an ounce in pre-rolled joints, blunts, and the like. But they won't be able to buy any of that weed legally.

The unusual situation is the result of political maneuvering by Congress to block Initiative 71, a ballot initiative to make marijuana possession legal for adults 21 and over that was approved in the November 2014 midterm election by 70 percent of DC voters.

A month after the initiative was approved, Congress, which controls DC's budget, intervened by adding a "rider" to a massive federal spending bill. This small additional clause, that is seemingly unrelated to the rest of the spending bill, tried to prevent local officials from using federal funds to implement the initiative. Paradoxically, the same legislation also contained another amendment to stop the federal government from interfering with state medical marijuana industries.

Thanks to Congress, entrepreneurs that hoped to take advantage of marijuana legalization in DC — the fourth part of the US to legalize the drug after Washington, Colorado, Oregon, and Alaska — might have to shelve their business plans, at least for a little while.

For the past 30 days, DC's legalization plan has been undergoing a congressional review, which concludes Thursday. The end result will likely be that pot becomes legal but virtually unregulated in DC, meaning people will be trading — or "gifting" — their weed in a hazy zone of legal uncertainty.

Morgan Fox, spokesman for the Marijuana Policy Project, an organization working to end pot prohibition, told VICE News that the policy gap between legalization and regulation is a misguided attempt by Congress to score political brownie points with their voters at the expense of states' rights.

"We see this all the time — Congress using DC as a bully pulpit to enforce rules to gain political points with their constituents," Fox said. "But in this case, DC voters overwhelmingly voted in favor of legalization."

Nationwide, marijuana remains banned under federal law and is still considered a Schedule I controlled substance, along with LSD, heroin, and other drugs that have no perceived medical value in the eyes of the government. A Department of Justice (DOJ) memorandum issued last year, however, essentially said the feds would take a hands-off approach to enforcement in states that voted to legalize pot — so long as they follow a few federal guidelines.

But the rider now prevents local lawmakers in DC from spending money to "enact any law, rule, or regulation to legalize or otherwise reduce penalties" relating to pot.

Without the funds to establish "regulatory and enforcement systems," Congress has effectively blocked local authorities from regulating and taxing the pot industry, which DC budgeters have estimated could generate $130 million in annual revenue.

Despite the federal move to block legalization, DC Attorney General Karl Racine argued that the spending rider cannot retroactively halt the enactment of Initiative 71. DC Council Chairman Phil Mendelson, a Democrat, submitted the policy for a mandatory 30-day congressional review in January.

DC council member David Grosso also quietly introduced new legislation in January to tax and regulate pot like alcohol and create a framework for licensed cultivators, product manufacturers, retail stores, and testing labs in the District. But that bill is on hold as the council continues to seek a way around Congress' rider.

"We have a battle on our hands whenever [Congress] thinks they can come in and influence us and how we govern ourselves," Grosso told VICE News in December. "This is a blow to DC in general, a blow to home rule and our freedoms and democracy. Its frustrating."

At this late stage, it appears Initiative 71 will survive the review by Congress.

"From everything that we've heard, [blocking the initiative] is not even on the leadership's radar," Fox said. "They have way more important issues to deal with."

Congress has only moved to override DC laws three times in the past 40 years. Overriding the law would also require the approval of President Barack Obama, who said in January that, although marijuana remains illegal under federal law, his administration is "not going to spend a lot of resources trying to turn back decisions that have been made at the state level on this issue." Obama has also documented his own past marijuana use in his autobiography.

Obama may have helped nudge along regulation laws in DC with the addition of a single word to his federal spending bill unveiled earlier this month.

By adding the word "federal" to the portion of his $4 trillion budget proposal that blocks the use of "federal funds" to implement marijuana laws, he left the door ajar for DC's city council to regulate and legalize marijuana on its own dollar. If the wording makes it through the final version of the budget, which still needs to be approved by the Republican-controlled House and Senate, new rules on marijuana sale and taxation could be in place in the District by the end of the year.

'Now that marijuana is going to be legal soon, we're going to see a lot less legal enforcement and arrest rates go down.'

Alaska, meanwhile, saw its own ballot initiative ending pot prohibition for adults take effect on Tuesday. Similar to the situation in DC, state lawmakers have yet to establish a regulatory framework that dictates how the drug will be sold and taxed. State lawmakers introduced the first legislation on the issue Monday.

"While regulation has stalled, I think what we're going to see in DC is a little bit of the illicit market disappearing," said Fox. "The biggest difference is going to be enforcement. The current drug laws were disproportionately targeting young African American men, so now that marijuana is going to be legal soon, we're going to see a lot less legal enforcement and arrest rates go down."

But laws that regulate recreational marijuana could also have unintended consequences on the medical marijuana industry. DC is among 32 states that currently have some type of medical marijuana law on the books, with at least a dozen others currently weighing similar legislation.

Mike Liszewski, government affairs director for medical marijuana advocacy group Americans for Safe Access, said that medical pot, edibles, and other products are a little more expensive in DC because the District has limited cultivation sites to 500 plants.

Limited terrain in the US capital, which is a little less than 70 square miles, means there's "not a whole lot of land that is available for cultivation use," Liszewski said. He added that current federal law prevents DC from importing marijuana from other states, which could lead to a shortage as demand continues to sprout.

"One issue we are experiencing here in DC is making sure there's enough marijuana being grown to serve the patient population," Liszewski said. "Currently there are 1,500 plants and about 2,500 patients. It's going to be difficult to supply the medical patient population and recreational population with that amount."

'Conservative politicians are all for states' rights and limited government until you get to drug policy.'

Removing the barriers for marijuana transportation and access across all states could potentially solve that issue. Last Friday, two members of Congress introduced separate House bills that would effectively legalize and regulate the drug on a national level.

Colorado Democrat Jared Polis's Regulate Marijuana Like Alcohol Act seeks to do just what its name suggests, and would also remove pot from the list of Schedule I controlled substances. Democrat Earl Blumenauer's Marijuana Tax Revenue Act would provide for a federal levy on regulated pot sales, incentivizing Congress to vote for legalization.

"It is time for us to replace the failed prohibition with a regulatory system that works and let states and municipalities decide for themselves if they want, or don't want, to have legal marijuana within their borders," Polis said in a statement.

Fox said he is not sure whether the bills will capture enough votes, but they are at least "moving the conversation along nationally." He also said that conservative anti-pot lawmakers — many of them Republicans who currently control Congress — may be forced soon to make tough choices as voter opinion rapidly shifts in favor of legalization.

Some of these politicians will be caught between wanting to legislate based on hardline anti-marijuana stances and deeply held aspirations to preserve states' rights and block federal government interference, he said.

"Conservative politicians are all for states' rights and limited government until you get to drug policy," Fox added. "But the pendulum is starting to swing and they are starting to see that their constituents are voting for marijuana regulation and policy."

VICE News' Olivia Becker contributed to this report.