Abstract: In a state that has legalized marijuana, does a state officer have probable cause to conduct a warrantless search of a vehicle based on the smell of marijuana alone, because marijuana is still prohibited under federal law? This Article is the first to consider that unsettled question. Over the last ten years, almost every state has altered the legality of marijuana in some way, either through decriminalization or legalization. Yet the possession, use, and cultivation of marijuana continue to be illegal at the federal level. Prior to these reforms, state courts generally upheld warrantless searches of vehicles based on nothing more than an officer smelling marijuana on the assumption that, because marijuana was illegal in all forms, the plain smell of marijuana alone gave officers sufficient probable cause to believe that the vehicle contained evidence of a crime. This is often referred to as the plain smell doctrine. In most states that have legalized marijuana, however, smell alone is no longer sufficient to establish probable cause. Despite the shifting legal landscape, some state officers continue to conduct warrantless car searches because marijuana remains illegal under federal law.
The Supreme Court has never considered this cross-enforcement issue, and lower courts are inconsistent in addressing it. This Article argues that even if lower courts remain divided or the Supreme Court eventually rules cross-enforcement constitutional, states retain the power to protect the intent of their marijuana legalization reforms. States that have legalized marijuana can protect that policy choice by enacting laws that partially or entirely block cross-enforcement by means outside the Fourth Amendment. That means states can opt out of cross-enforcement regardless of the Fourth Amendment inquiry. Despite some limitations, this proposal has the benefit of protecting state policy choices while also encouraging safer, more effective, and less biased policing.
