USPS Shipping Restrictions: Prohibited and Restricted Items (2026)

USPS divides unmailable items into three categories: prohibited (never under any circumstances), restricted (allowed under specific conditions), and hazardous materials/hazmat (allowed with proper packaging and labeling). The authoritative source for all three is USPS Publication 52 — Hazardous, Restricted, and Perishable Mail.

Since 2026, USPS sorting centers use AI-enhanced parcel scanning to detect prohibited items. Don’t rely on items slipping through undetected — the consequences include postal inspectors, fines, and potentially federal charges.

Quick Reference: Common Items and Their Status

Prohibited Items: No Exceptions

These items cannot be mailed through USPS under any circumstances:

Marijuana. USPS operates under federal law. Marijuana is a Schedule I controlled substance regardless of state legalization. Postal inspectors can obtain a warrant to open packages suspected of containing marijuana. Penalties include fines and federal charges.

Handguns and concealable firearms. Individuals (non-licensed) cannot mail handguns domestically. Even with a license, handguns require specific shipping procedures. Rifles and shotguns have separate rules (see Restricted section).

Gasoline and flammable liquids. Includes gasoline, diesel, lighter fluid, and other flammable or combustible liquids.

Explosives. Any material classified as an explosive by the Department of Transportation. This includes fireworks, flares, and certain pyrotechnic devices.

Poison (Class A and B toxins). Highly toxic substances with immediate danger to life.

Alcohol (most domestic cases). Beer, wine, and liquor cannot be sent through USPS by private individuals. Licensed alcohol shippers have extremely limited exceptions.

Restricted Items: Conditions Apply

These items can be mailed but require specific packaging, labeling, or documentation:

Lithium Batteries

The lithium battery rules catch many e-commerce sellers off guard.

New lithium batteries installed in devices (laptops, phones, cameras): These can ship by air domestically with no special requirements beyond what the carrier normally handles. Internationally, quantity and watt-hour limits apply — follow IATA DG regulations.

Pre-owned, damaged, defective, or recalled batteries: Must be sent by surface transportation only (not air mail, not Priority Mail Express air segments). Package must be labeled “Restricted Electronic Device” and “Surface Transportation Only.” USPS can return these if sent by air service.

Standalone lithium batteries (not in a device): Treated as hazmat. Quantity limits, surface transport only, specific inner and outer packaging requirements.

Firearms (Long Guns)

Rifles and shotguns can be mailed by licensed manufacturers and dealers (FFLs), and by individuals mailing to a licensed dealer for repair. The firearm must be unloaded, packaged to prevent accidental discharge, and labeled “Firearms” on the outer packaging.

Individuals cannot mail firearms to other individuals. All firearm transfers must go through an FFL.

Hemp and CBD Products

Hemp-derived products containing 0.3% THC or less by dry weight are mailable domestically under the 2018 Farm Bill, but USPS requires documentation: the shipper must have a license or authorization to produce the product, and must provide documentation that the product meets the THC threshold. Without documentation, USPS treats the package as containing marijuana.

Aerosols

Non-flammable aerosols (e.g., deodorant, air freshener, sunscreen sprays) can be shipped domestically by surface transport with quantity limits. Flammable aerosols (spray paint, lighter fuel aerosols) are prohibited. Internationally, most aerosols are prohibited regardless of flammability.

Liquids

Non-hazardous liquids are mailable with specific packaging requirements: the container must be sealed and cushioned with absorbent material sufficient to contain the entire liquid volume if the container breaks. The outer packaging must not leak or show signs of the liquid.

Hazardous liquids (flammable, corrosive, oxidizing) are prohibited.

Prescription Drugs

Prescription drugs can be mailed only by authorized entities (licensed pharmacies mailing to patients, physicians mailing to patients under their care). Individuals cannot mail prescription drugs to other individuals. Controlled substances have additional DEA regulations.

Size and Weight Limits by Service

Packages exceeding the maximum length + girth for Priority Mail are assessed a “balloon” surcharge.

What Happens If You Mail a Prohibited Item

USPS Postal Inspection Service (USPIS) is a federal law enforcement agency with authority to open mail under warrant. Prohibited items can result in:

• Package seizure and destruction
• Criminal referral to federal prosecutors
• Fines starting at $10,000 for hazmat violations
• Federal charges for prohibited controlled substances

The “it probably won’t get caught” calculation has changed with AI-enhanced scanning at major distribution centers. Don’t ship prohibited items.

And if the item is mailable but cannot go through a blue box or kiosk, where to drop off USPS packages covers which items must go straight to the counter.

Frequently Asked Questions

Can I ship alcohol through USPS? Generally no. USPS prohibits domestic alcohol shipments for private individuals. Licensed manufacturers and dealers can ship under extremely limited circumstances. For direct-to-consumer wine and spirits shipping, FedEx and UPS have carrier programs for licensed shippers that USPS does not offer. If your real item is fragrance rather than beverage alcohol, the USPS perfume shipping guide is the more relevant rule set.

Can I mail a knife or sword through USPS? Yes, with restrictions. Knives must be packaged so that sharp edges cannot pierce the outer packaging and cannot injure handlers. Blades should be sheathed or blunted. Switchblades and gravity knives have additional restrictions.

Can I ship a vape pen or e-cigarette through USPS? No. PACT Act amendments prohibit USPS from delivering e-cigarettes, vaping devices, and related accessories to consumers. Licensed retailers face extremely limited exceptions.

Can I mail dry ice? Yes, with restrictions. Dry ice is permitted as a refrigerant in packages shipping perishables. The package must be marked “Dry Ice” with the net weight of the dry ice, and must be packaged to allow CO2 to vent. Maximum quantity limits apply.

Are there restrictions on mailing food through USPS? Non-perishable food can be shipped without restrictions. Perishables (meat, dairy, fresh produce) are mailable with proper packaging — insulated containers, sufficient coolant to last the transit time — but USPS holds shippers responsible if the contents spoil. Fresh fruits and vegetables are prohibited internationally.