Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

Nebraska and Oklahoma on Thursday asked the U.S. Supreme Court to declare Colorado's legalization of marijuana unconstitutional, saying the drug is being brought into the neighboring states.

Nebraska Attorney General Jon Bruning said the states filed a lawsuit seeking a court order to prevent Colorado from enforcing the measure known as Amendment 64, which was approved by voters in 2012. The complaint says the measure runs afoul of federal law and therefore violates the Constitution's supremacy clause, which says federal laws trump state laws.

"This contraband has been heavily trafficked into our state," Bruning said at a news conference in Lincoln. "While Colorado reaps millions from the sale of pot, Nebraska taxpayers have to bear the cost."

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

In a policy statement last year, the U.S. Justice Department noted it doesn't have the resources to police all violations of federal marijuana law. It laid out eight federal law enforcement priorities that states need to protect if they want to authorize "marijuana-related conduct." They include keeping marijuana in-state — something Oklahoma and Nebraska says Colorado has failed to do.

Oklahoma Attorney General Scott Pruitt said Colorado's decision has hindered his state's efforts to enforce its anti-marijuana laws. Colorado Attorney General John Suthers said the lawsuit was without merit but that he was not surprised by it because neighboring states have expressed concerns about Colorado marijuana crossing the border.

"However, it appears the plaintiffs' primary grievance stems from non-enforcement of federal laws regarding marijuana, as opposed to choices made by the voters of Colorado," Suthers said in a statement in which he said Colorado would vigorously defend its law.

Legal scholars say it's too early to know how the Supreme Court might handle the case or if it will even accept it.

IN-DEPTH

— The Associated Press