Arguing that two neighboring states are dangerously meddling with Colorado’s marijuana laws, state Attorney General Cynthia Coffman on Friday urged the U.S. Supreme Court to reject a landmark lawsuit filed by Nebraska and Oklahoma over marijuana legalization.

In a brief submitted in response to the lawsuit, Coffman wrote that Nebraska and Oklahoma “filed this case in an attempt to reach across their borders and selectively invalidate state laws with which they disagree.”

The two states’ lawsuit seeks to strike down Colorado’s licensing of recreational marijuana stores. Nebraska and Oklahoma officials argue that the stores have caused a flood of marijuana into their states, stretching their law enforcement agencies thin and threatening their sovereignty.

But Coffman argued the lawsuit, if successful, would only worsen problems involving black-market marijuana in all three states. Colorado’s regulations for marijuana stores “are designed to channel demand away from this black market and into a licensed and closely monitored retail system,” she wrote.

If the stores are closed, Colorado would be left with laws that legalize marijuana use but do not regulate its supply.

“This is a recipe for more cross-border trafficking, not less,” Coffman wrote.

DOCUMENT: Read Colorado’s Supreme Court brief defending marijuana legalization

Friday’s brief is the first time Colorado officials have had to make a full-throated argument in favor of the state’s marijuana legalization laws. In doing so, the brief spends several pages noting states’ lengthy history of trying to regulate marijuana, “a product whose use is staggeringly widespread.” Nearly half of all states now have laws legalizing recreational or medical use of marijuana, the brief states.

In addition to Coffman, Colorado’s solicitor general and four other lawyers at the attorney general’s office are listed as authors of the brief.

Nebraska and Oklahoma filed their lawsuit directly with the Supreme Court because it involves a dispute between states. Before the lawsuit gets a hearing, the nation’s highest court must first decide whether to take up the case. There is no timeline for the decision.

The lawsuit does not challenge Colorado’s laws for medical marijuana use or sales, nor does it seek to strike down laws legalizing recreational marijuana use and possession. Instead, Nebraska and Oklahoma argue in the lawsuit that Colorado’s licensing of marijuana stores “has created a dangerous gap in the federal drug control system.”

“Marijuana flows from this gap into neighboring states, undermining Plaintiff States’ own marijuana bans, draining their treasuries, and placing stress on their criminal justice systems,” the lawsuit alleges.

In a statement Friday, Coffman — a Republican who opposed marijuana legalization — said she shares Nebraska and Oklahoma’s concerns about illegal marijuana trafficking.

Coffman’s brief, though, pins the blame for that trafficking not on Colorado’s marijuana stores but on “third parties who illegally divert marijuana across state lines.” The brief points to the recent indictments of 32 people accused in a massive marijuana-smuggling ring as evidence that Colorado authorities are continuing to bust traffickers.

Colorado’s laws received support Friday from Coffman’s counterparts in Washington state and Oregon — where recreational marijuana is also legal.

In a friend-of-the-court brief filed Friday in support of Colorado’s laws, Washington and Oregon attorneys general argue that Colorado’s laws don’t hurt Nebraska and Oklahoma’s abilities to enforce their own laws.

“Nebraska and Oklahoma retain the constitutional powers of every other sovereign State in the nation,” the brief argues. “They can investigate and prosecute persons who violate their laws; neither is powerless to address marijuana within their borders.”

The interstate lawsuit is the most high-profile of four cases that have been filed against marijuana legalization in Colorado.

The three other lawsuits — two by Colorado residents upset about marijuana businesses moving nearby and one by several Colorado sheriffs who believe marijuana legalization forces them to violate their oath of office — are pending in federal district court in Denver.

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/johningold