The U.S. Supreme Court on Monday declined to hear a lawsuit brought by Nebraska and Oklahoma over Colorado’s system of legalized recreational marijuana, according to NPR. Nebraska and Oklahoma said they are having trouble protecting their borders from the increased flow of marijuana.

In December, the federal government advised the Supreme Court to avoid weighing in on the lawsuit, which asked to block Colorado’s legal marijuana system. The states said Colorado’s law legalizing recreational marijuana is unconstitutional and places a burden on their criminal justice systems.

The suit argued that because marijuana is illegal at the federal level, Colorado’s system violates federal interstate commerce laws and the Controlled Substances Act. Colorado asked the court to throw out the case. Last spring, the Supreme Court asked for the Obama Administration’s view on the suit.

The court did not explain its decision, the article notes. Justices Samuel Alito and Clarence Thomas disagreed with the decision. In a dissent, Thomas wrote that Nebraska and Oklahoma’s claims of “significant harms to their sovereign interests” should have been permitted to proceed, and should not have been denied without an explanation.

In a statement, Nebraska Attorney General Doug Peterson said, “Today, the Supreme Court has not held that Colorado’s unconstitutional facilitation of marijuana industrialization is legal, and the Court’s decision does not bar additional challenges to Colorado’s scheme in federal district court.” Peterson’s office said their office is “working with its partners in Oklahoma and other states to determine the best next steps toward vindicating the rule of law.”