As of 15 October 2008, US Customs & Border Protection requires that all laden containers entering the US by sea must have seals which meet the ISO/PAS 17712 standard. This ruling is in effect for all cargo bound for the US, whether as a destination or passing through the country. In addition, the details of seal numbers must be included in the Vessel Automated Manifest System (AMS) sent to the CBP at least 24 hours before the ship's departure for the US.

The ISO standard states that seals must not only be strong, but also uniquely and irreversibly marked; seals which are compliant with the standard are subject to tensile, shear, impact, and bending tests. It is important that the manufacturer is approved, so buyers must watch out for counterfeit seals on sale. The standard also requires that it is impossible to tamper with a seal without leaving readily apparent traces. Evidence of tampering includes a frayed appearance of cable or wire seals, or scratches on bolt, rod or padlock-type seals.

The seals should, if possible, be placed on the seal brackets which are on the door sill and the bottom of the locking bar (if they are fitted) rather than on the higher seal brackets which are on the locking bar and the door. Some older containers do not have this facility. This prevents thieves removing the locking bar handle hub rivet, opening the doors without disturbing the seal and after stealing, putting the rivet back in its place, gluing it in.

The shipper or consolidator should ensure that only authorised staff control the use of seals and ensure that the seal is fixed to the container once stuffing is complete. The Club has had experiences where the truck driver has been left to fit the seal at the shipper's premises and deliberately not snapped it shut. In transit the container was opened, cargo stolen and then the seal applied properly. Ideally, the details of seals should also be recorded at nodal points in the supply chain and physically checked for integrity.

It is understood that empty containers are not subject to the new CBP requirement, and can be left unsealed, as can tank containers, open-tops and those which cannot accommodate a seal. For C-TPAT participants these regulations are not new; however, they are now required of all containers entering the US by sea. CBP may assess civil penalties against a party responsible for violation of the sealing requirements, including detaining the ship.