Marijuana plants are seen hanging to dry in an undated handout picture taken in Colorado and released by the U.S. Department of Justice October 8, 2015. REUTERS/U.S. Department of Justice/Handout via Reuters

WASHINGTON (Reuters) - President Barack Obama’s administration asked the U.S. Supreme Court on Wednesday to throw out a lawsuit filed by Oklahoma and Nebraska seeking to block Colorado’s voter-approved law legalizing recreational marijuana use by adults.

In their challenge to Colorado’s law, filed in December 2014, Nebraska and Oklahoma said marijuana is being smuggled across their borders and that drugs threaten the health and safety of children.

Nebraska and Oklahoma noted that marijuana remains illegal under federal law and said Colorado has created “a dangerous gap” in the federal drug control system.

Oklahoma and Nebraska’s lawsuit was filed under a rarely used Supreme Court process, known as “original jurisdiction,” in which the justices hear disputes between states that have not first been handled by lower courts.

U.S. Solicitor General Donald Verrilli said in court papers filed on Wednesday that the case was not the type of dispute the court would normally hear.

“Entertaining the type of dispute 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,” Verrilli said.

The Obama administration has allowed states to experiment with marijuana legalization even though the drug remains illegal under federal law.

Colorado voters legalized recreational marijuana use in 2012. Washington state also voted the same year to legalize recreational marijuana use by adults. Oregon, Alaska and the District of Columbia followed suit in 2014.