The US Supreme Court on Monday declined to hear a case filed by the states of Nebraska and Oklahoma to have Colorado’s recreational marijuana laws declared unconstitutional.

The justices have not commented on the decision to throw out the lawsuit, which Nebraska and Oklahoma filed directly in Supreme Court against the neighboring state. The suit contends that Colorado’s law allowing adults recreational use of marijuana violates federal antidrug regulations. The two states further argue that Colorado-sourced pot is spilling over their borders, impeding their anti-drug efforts and eating into their resources.

“In passing and enforcing Amendment 64, the state of Colorado has created a dangerous gap in the federal drug control measures enacted by the United States Congress,” the lawsuit reads. “Marijuana flows from this gap into neighboring states, undermining [their] own marijuana bans, draining their treasuries, and placing stress on their criminal justice systems.”

Nebraska and Oklahoma further argued that marijuana and other drugs threaten public health and safety, especially of children.

The court declined to hear the case in an unsigned opinion. Conservative justices Clarence Thomas and Samuel Alito dissented, with Thomas writing that “the plaintiff states have made a reasonable case.”

The high court’s decision comes amid a shifting atmosphere around pot use nationwide. Even as four states and the District of Columbia have legalized recreational marijuana, for instance, “concerns about children getting access and their exposure to secondhand smoke as well as other the societal effects of marijuana still run deep in some parts of the country,” the Monitor reported in November.

Medical marijuana also faces challenges around consistency, quality control, and consumer safety as states struggle to regulate the fast-growing industry.

Still, Colorado stands by its law – and the Obama administration had sided with the state, despite the federal government’s opposition to marijuana legalization.

Colorado added that the Supreme Court was not the right place to take the case. The lawsuit was filed under the court’s “original jurisdiction,” in which the high court justices consider disputes between states that are not first heard by lower courts. Such lawsuits often take place between states fighting over their borders or over shared use of water from rivers that flow through multiple states.

Tom Angell, chairman of the Marijuana Majority advocacy group, applauded the court’s decision.

“At the end of the day, if officials in Nebraska and Oklahoma are upset about how much time and resources their police are spending on marijuana cases, as they said in their briefs, they should join Colorado in replacing prohibition with legalization,” Mr. Angell said.

“That will allow their criminal justice systems to focus on real crime, and it will generate revenue that can be used to pay for healthcare, education and public safety programs,” he added.

This report contains material from The Associated Press and Reuters.