The U.S. Supreme Court on Monday declined to hear Nebraska and Oklahoma’s proposed lawsuit against Colorado’s legal marijuana laws.

The 6-2 vote means the nation’s highest court will not rule on the interstate dispute, and Colorado’s legal cannabis market is safe — for now.

“Since Colorado voters overwhelming passed legal recreational marijuana in 2012, we have worked diligently to put in place a regulatory framework — the first in the world — that allows this new industry to operate while protecting public health and safety,” Colorado Gov. John Hickenlooper said in a statement Monday. “With today’s Supreme Court ruling, the work we’ve completed so far remains intact.”

The Supreme Court ruling was the latest in a string of losses in court for those challenging Colorado’s first-of-its-kind cannabis laws:

• A U.S. district judge on Monday dismissed a racketeering suit filed on behalf of Pueblo County horse ranchers who complained that a marijuana cultivation facility marred their view.

• In late-February, a different U.S. District judge dismissed a lawsuit filed on behalf of sheriffs and attorneys in Colorado, Nebraska and Kansas.

• In December, another RICO suit involving the Holiday Inn in Frisco was dismissed after the marijuana business in question shut its doors and two related companies settled for $70,000.

“The takeaway from all this,” said attorney Matthew Buck, who represented six defendants in the Pueblo County suit, “is that the federal district court realizes that the voters of Colorado are informed, intelligent and they’re not going to let outside interests govern what happens inside the state of Colorado.”

Three of the four marijuana lawsuits filed against Colorado officials and businesses were organized and partially funded by out-of-state anti-drug organizations and socially conservative law firms, a Denver Post investigation revealed in January.

Because the Supreme Court has passed on the case, Nebraska and Oklahoma could now take it to a federal district court if they choose to, law experts say — something the states’ attorneys general hinted at on Monday .

“The complaint, on its face, presents a ‘controvers[y] between two or more States’ that this Court alone has authority to adjudicate,” Supreme Court Justice Clarence Thomas wrote in the dissenting opinion. “The plaintiff States have alleged significant harms to their sovereign interests caused by another State. Whatever the merit of the plaintiff States’ claims, we should let this complaint proceed further rather than denying leave without so much as a word of explanation.”

Justice Samuel A. Alito Jr. joined Thomas in dissenting. The majority offered no opinion to accompany the decision.

READ: See Justice Clarence Thomas’ dissent in the pot case

Nebraska Attorney General Doug Peterson said he was disappointed, but that he is working with partners in Oklahoma “and other states” to figure out their next steps “toward vindicating the rule of law,” according to a statement.

“Today, the Supreme Court has not held that Colorado’s unconstitutional facilitation of marijuana industrialization is legal,” Peterson said in the statement, “and the Court’s decision does not bar additional challenges to Colorado’s scheme in federal district court.”

Oklahoma Attorney General Scott Pruitt added: ” The fact remains — Colorado marijuana continues to flow into Oklahoma, in direct violation of federal and state law. Colorado should do the right thing and stop refusing to take reasonable steps to prevent the flow of marijuana outside of its border. And the Obama administration should do its job under the Constitution and enforce the Controlled Substances Act. Until they do, Oklahoma will continue to utilize every law enforcement tool available to it to ensure that the flow of illegal drugs into our state is stopped.”

Colorado Attorney General Cynthia H. Coffman celebrated the victory but also acknowledged that Nebraska and Oklahoma’s concerns won’t disappear with the court’s ruling.

“Although we’ve had victories in several federal lawsuits over the last month, the legal questions surrounding Amendment 64 still require stronger leadership from Washington,” Coffman said in the statement.

While the attorneys general were all hoping for more federal guidance, legal experts aren’t surprised they got so little.

“Neither the current administration nor the Supreme Court is itching for this fight,” said Sam Kamin, a University of Denver law professor focusing on cannabis law. “One after the other, the legal challenges are failing. Some are failing on their merits. One is failing because the Supreme Court didn’t express interest. But there have been very few, if any, outright wins for those seeking to challenge Colorado’s marijuana.”

Legalization activists reacted positively to the court’s decision.

“There’s no question about it: This is good news for legalization supporters,” said advocate Tom Angell, chairman of Marijuana Majority. “This case, if it went forward and the Court ruled the wrong way, had the potential to roll back many of the gains our movement has achieved to date. And the notion of the Supreme Court standing in the way could have cast a dark shadow on the marijuana ballot measures voters will consider this November.”

Nebraska and Oklahoma filed the proposed lawsuit more than a year ago, and it specifically challenges Colorado’s ability to license and regulate marijuana businesses. The two states say Colorado’s system impermissibly conflicts with federal law and creates burdens for them by increasing the amount of pot coming across their borders.

Because the matter involves a dispute between states, it was filed directly to the Supreme Court. The first step in the lawsuit was for the justices to decide whether they even wanted to consider it. When the Supreme Court does accept such cases, the subsequent litigation can go on for years or even decades.

Attorneys for both the state of Colorado and the Obama administration had urged the court not to take up the lawsuit, while a group of former leaders of the Drug Enforcement Administration sided with Nebraska and Oklahoma and asked the court to accept the case.

In 2012, Colorado voters legalized possession of small amounts of marijuana and also authorized the creation of state-administered rules that would allow stores to sell marijuana to anyone over 21 years old. Those stores opened in 2014, and, since then, Nebraska and Oklahoma say they have seen an increased number of people bringing marijuana into their states, in violation of both their state laws and federal law.

“The State of Colorado has created a dangerous gap in the federal drug control system,” the two states complained in their lawsuit.

Coffman responded that eliminating the stores — while keeping marijuana possession legal — would likely create more trafficking. And, the Obama administration, in its own filing, said the case was inappropriate for the Supreme Court because the harm is allegedly being caused by individual lawbreakers, not the state of Colorado, itself.

“Entertaining the type of dispute at issue here — essentially that one State’s laws make it more likely that third parties will violate federal and state law in another State — would represent a substantial and unwarranted expansion of this Court’s original jurisdiction,” U.S. Solicitor General Donald Verrilli Jr. wrote in his brief to the court.

The Supreme Court justices spent more than a year pondering whether to take the case. The proposed lawsuit was scheduled and re-scheduled five times for a closed-door conference, where the justices would debate the merits of taking the case.

Ricardo Baca: 303-954-1394, rbaca@denverpost.com or @bruvs. John Ingold: 303-954-1068, jingold@denverpost.com or @johningold