Directly from Cigars International:
Note: Due to FAA regulations, lighters must be shipped via ground parcel services. Express shipping is not available.
So, the way I interpet that statment, that includes ANY carrier that ships ground, including UPS and DHL ground services.
Violations of the Federal Hazardous Materials Regulations (HMR) can result in severe penalties of up to $27,500 per violation, and often multiple violations can occur with just a single shipment. Unfortunately lighers containing butane are listed under the HMR.
Due to the various requirements, the shipper must mark the shipment with the proper shipping name and UN identification number; label the shipment with the proper label for the contents, as well as orientation arrows for liquid shipments or a "CARGO AIRCRAFT ONLY" label when the material cannot be carried on a passenger-carrying aircraft; use correct specification packaging; declare the Hazmat to the carrier; and to certify that the contents are properly classed and in condition for shipment. In addition, violations occur when, for example, there is a release of the material to the environment, quantity limitations are exceeded, or there was a failure to train the persons handling the shipment.
Cigarette lighters or similar devices (such as mini-or micro-torches) equipped with an ignition element and containing gaseous fuel are regulated under the HMR as Lighters or Lighter refills and subject to the provisions of Secs. 173.21 and 173.308. Section 173.21 forbids the transportation of packages containing a cigarette lighter or similar device equipped with an ignition element and containing fuel, except that a cigarette lighter or a similar device may be shipped if the design of the device and its inner packaging has been examined by an approved laboratory, and specifically approved by the Associate Administrator for Hazardous Materials Safety. Transportation
regulations which apply to these devices include fuel capacity and filling limits, pressure capability of the device, and packaging restrictions. Devices containing a flammable gas must conform to the
quantity limits and packaging requirements specified in Sec. 173.308.
Carriers, such as United Parcel Serice or FedEx Ground must know what is contained within the package that is being shipped. Failure to inform the carrier can result in them being held liable for an undeclared shipment of hazardous materials, with possible imposition of the penalties.