Since September 11, 2001, thousands of merchant ships have been boarded by U.S. Navy sailors. Its all about looking for terrorists, but many of the suspicious ships targeted for boarding are just ordinary smugglers, or completely innocent. These guys often dont like the law in general, but are not about to pick a fight with an American warship. So they show their displeasure in other ways. Many have taken to stringing barbed wire along the deck railings. American boarding parties have taken to carrying wire cutters with them because of this. Other suspicious skippers have strung cables from the deck to masts and cranes. This makes it difficult for a boarding party to come in by rappelling down from a helicopter. Now thats spite.

Other merchant seamen have invented some more practical problems for boarding parties. A common one is welding shut hatch covers and doors to areas they dont want the law looking at. This forces a well prepared boarding party to have welders on call to get into these areas. A messier way to create a lack of access was found in ships where barrels of grease, oil or other slippery liquids were placed around the ship, near passages leading to forbidden areas. As the boarding party came aboard, the barrels and buckets were knocked over, leaving the boarding party to deal with the slippery situation as best they could. 

The U.S. Navy has responded by working with the various coast guards and port officials in the areas they are patrolling, to exchange information on the suspicious, and uncooperative, characters they run into. Smugglers tend to move among a small number of ports, or coastal villages, where they pick up and drop off material. So the American ship captains let it be known that bad behavior will be repaid. American naval officers are not obliged to report, to the local authorities, everything their boarding parties find. But give the boarding party a hard time, and you can expect trouble from the local law in the next port you enter.