THP Interdiction Plus Unit — I-40 / I-65 / I-75 / I-24

Last verified: May 2026

What Interdiction Plus Is

The Tennessee Highway Patrol (THP) is the state's primary highway-traffic-enforcement agency, operating under the Tennessee Department of Safety and Homeland Security. Within THP's broader troop structure sits the Interdiction Plus Unit, a specialized drug-trafficking task force whose mission is to identify and disrupt the movement of bulk illicit narcotics — including but not limited to marijuana, methamphetamine, fentanyl, cocaine, and heroin — on Tennessee's interstate corridors.

Interdiction Plus is supported by the THP Criminal Investigations Division (CID), which provides investigative follow-up and case-building beyond the initial roadside stop. It partners formally with the Tennessee Bureau of Investigation (TBI), the Drug Enforcement Administration's Memphis and Nashville offices, and county sheriffs through standing task-force agreements. K-9 teams are central to the unit's operational model.

The Four Primary Corridors

Interdiction Plus deploys principally on Tennessee's four interstate spines:

• I-40 (Memphis ↔ Nashville ↔ Knoxville ↔ Bristol): the east-west spine of the state and the most active cannabis-trafficking corridor. THP press releases regularly describe seizures in the 20-to-150-pound range on I-40 in West Tennessee, particularly in the Lauderdale, Tipton, Haywood, and Madison county stretches. The Memphis-to-Nashville segment is the principal eastbound route for Missouri Bootheel and West Memphis source product moving into middle Tennessee. The Knoxville-to-Bristol segment is the principal eastbound route from middle Tennessee toward the EBCI Qualla Boundary and Virginia.
• I-65 (Nashville's N-S corridor): the route from Kentucky south through Nashville to Alabama. Used historically by Indiana and Michigan-source product moving south. The Robertson, Sumner, and northern Davidson county segments draw active deployment.
• I-75 (Chattanooga ↔ Knoxville): the north-south through East Tennessee from Atlanta toward the Cumberland Gap.
• I-24 (Chattanooga ↔ Nashville ↔ Clarksville): connects southeastern Tennessee through Nashville toward Fort Campbell and the Kentucky line.

The Stop Mechanics

Interdiction Plus operates within the constitutional framework established by Whren v. United States, 517 U.S. 806 (1996) (any traffic violation provides constitutional basis for stop regardless of subjective officer motivation), Illinois v. Caballes, 543 U.S. 405 (2005) (K-9 sniff during lawful traffic stop does not require independent probable cause), and Rodriguez v. United States, 575 U.S. 348 (2015) (officers may not extend a traffic stop beyond what is necessary to address the traffic violation absent independent reasonable suspicion).

Typical stop sequence:

• Initial stop on traffic-violation pretext (speeding, lane violation, equipment defect, following too closely).
• Officer observation of "indicators of criminal activity" — nervous demeanor, inconsistent travel narratives, masking odors, single keys on rental contracts, third-party rental vehicles, multiple cell phones, lived-in appearance of vehicle.
• K-9 deployment during the lawful stop window.
• K-9 alert → probable cause for vehicle search under the automobile exception (Carroll v. United States, 267 U.S. 132 (1925)).
• Discovery of contraband → arrest, vehicle seizure under T.C.A. § 53-11-451 civil-asset-forfeiture authority, charging.

The Smell-as-Probable-Cause Doctrine — Increasingly Fraught

Tennessee courts have continued to recognize the alleged smell of marijuana as sufficient probable cause for an automobile-exception search. The doctrine has become increasingly fraught given the indistinguishability of legal hemp from prohibited marijuana — both produce identical odor profiles to human nose and to most K-9s. Some Tennessee state-court rulings post-2019 have narrowed the smell-only doctrine in light of legal hemp, but the doctrine remains generally available to officers, and Tennessee has not adopted the categorical smell-no-longer-sufficient rule that some other states' courts have embraced.

This matters at THP Interdiction Plus stops in two ways: (1) the $245M hemp-derived cannabinoid market means perfectly legal hemp products produce identical smells, complicating the post-stop search rationale; (2) post-Public Chapter 526 (effective January 1, 2026), legal hemp possession itself becomes more constrained, narrowing the legitimate-source explanation a motorist can offer.

Civil Asset Forfeiture — T.C.A. § 53-11-451

Tennessee law authorizes civil asset forfeiture of vehicles, cash, and property used to facilitate marijuana offenses under T.C.A. § 53-11-451. Following an Interdiction Plus stop where contraband is discovered, the vehicle is typically seized alongside any cash present. Reclamation requires the property owner to prevail in a separate civil-forfeiture proceeding — often more economically prohibitive than the cost of the vehicle itself, particularly for older vehicles or for cash sums under $10,000.

The unauthorized-substances tax under T.C.A. § 67-4-2801 et seq. (up to $3.50 per gram of marijuana and $50 per gram of concentrate, payable within 48 hours of acquisition) is routinely tacked onto interdiction cases as a basis for additional liens against seized property. See the forfeiture & paraphernalia page.

Out-of-State Plates & Returning Corridor Targeting

Out-of-state plates draw disproportionate scrutiny on Tennessee's returning corridors. Missouri plates entering Tennessee on I-55 from the Bootheel; Tennessee plates returning from Missouri, Arkansas, Mississippi, North Carolina, or Virginia; rental vehicles on I-40 with single-key contracts from western U.S. addresses — all draw stop attention. The pattern is well-documented in the THP press releases describing 20-to-150-pound seizures on I-40 in West Tennessee, where the source-state geography (Missouri, Arkansas) makes those weights consistent with bulk trafficking.

For personal-use cross-border consumers — the typical Memphis or Nashville resident returning with a single ounce or two of legal Missouri product — the Interdiction Plus profile is less central but still applies. The Funk and Mulroy DA declinations address misdemeanor simple possession; they do not preempt Tennessee state-law felony charging at >½ oz quantities, and they do not bind THP officers' arrest authority.

Working with the Governor's Task Force on Marijuana Eradication

Distinct from highway interdiction, the Governor's Task Force on Marijuana Eradication — administered by the THP and partnered with TBI, ABC, the Tennessee National Guard, and the Tennessee Wildlife Resources Agency — targets cultivation operations on the Cumberland Plateau and in Cherokee National Forest. Eradication seasons run summer through early fall, when outdoor grows are most visible from helicopter overflight. The Task Force and Interdiction Plus operate on different missions but share information and occasionally coordinate. See the Appalachian cultivation page.

Practical Posture for Tennessee Travelers

For travelers crossing Tennessee from Missouri, Mississippi, Arkansas, or the EBCI Qualla Boundary, the practical posture is to recognize that the I-40, I-55, I-65, I-75, and I-24 corridors are actively patrolled by a unit whose specific mission is interstate cannabis-trafficking interdiction. Traffic-violation pretexts include speeding, following-too-closely, lane violations, and equipment defects. Any K-9 alert — whether on legitimate marijuana smell, on legal hemp smell, or on cross-contamination from prior cargo — can ground a vehicle search. Returning home with cannabis from a legal jurisdiction subjects the consumer to Tennessee state-law penalties regardless of source.