Smuggling has existed ever since governments first attempted to control trade across their borders. Although it is often understood as an attempt to evade duties or taxes that the legislature has placed upon the importation of certain classes of goods, smuggling is a much broader phenomenon than this. It may apply to attempts to evade export regulations, for example, or trade in certain prohibited goods, such as weapons or drugs. People may be smuggled across frontiers. At one end of the spectrum, smuggling may be a highly organized criminal activity, or what some describe as "the smuggling industry;" at the other, it may consist simply of a sailor or passenger trying to slip something for personal use past the authorities. Consideration must also be given to attempts to evade regulations relating to internal trade. Taxes on this are classified as excise duties. At one time, compliance was enforced by excise officers, while international trade was policed by customs officers; latterly, the two revenue services have been merged into one.