In suing to stop marijuana legalization in Colorado, two neighboring states have embarked down an arcane legal pathway that could take years to reach a conclusion, legal scholars say. Nebraska and Oklahoma last week asked the U.S. Supreme Court to toss out portions of Colorado's pot legalization law. The states contend that Colorado's law — and especially Colorado's licensing and regulation of marijuana stores — violates the U.S. Constitution's Supremacy Clause, which says the federal law reigns when state and federal laws are in irreconcilable conflict.