Originally published December 18, 2014 at 2:03 PM | Page modified December 19, 2014 at 12:27 AM

Colorado's top law enforcement official promises to vigorously defend the state's historic law legalizing marijuana after Nebraska and Oklahoma asked the U.S. Supreme Court to declare it unconstitutional, saying the drug is freely flowing into neighboring states.

The two 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 and allows recreational marijuana for adults over 21. 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.

Colorado Attorney General John Suthers said the lawsuit was without merit.

"Because neighboring states have expressed concern about Colorado-grown marijuana coming into their states, we are not entirely surprised by this action," he said. "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."

The lawsuit says Colorado marijuana flows into neighboring states undermining their efforts to enforce their anti-marijuana laws.

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

Colorado has raised more than $60 million in taxes, licenses and fees from medical and recreational marijuana, which has been sold in stores since January.

The lawsuit says the sales have strained Nebraska and Oklahoma's finances and legal systems. Police are spending more time and money making arrests, housing inmates, impounding vehicles, seizing drugs and handling other problems related to Colorado pot.

Bruning, a Republican, blamed U.S. Attorney General Eric Holder for failing to enforce the federal law's ban on drugs in Colorado.

Read this article:

2 states challenge Colorado marijuana legalization