The conflict between state and federal law is, as of 2018, unresolved. The following individual drugs, listed under their respective family groups (e.g., barbiturates, benzodiazepines, opiates), are the most frequently sought after by drug users and as such are prohibited or otherwise heavily regulated for use in many countries:  The regulation of the above drugs varies in many countries. Alcohol possession and consumption by adults is today widely banned only in Islamic countries and certain states of India. The United States, Finland, and Canada banned alcohol in the early part of the 20th century; this was called Prohibition. Although alcohol prohibition was repealed in these countries at a national level, there are still parts of the United States that do not allow alcohol "sales", even though alcohol "possession" may be legal. Bhutan is the only country in the world where possession and use of tobacco is illegal. New Zealand has banned the importation of chewing tobacco as part of the Smoke-free Environments Act 1990. In some parts of the world, provisions are made for the use of traditional sacraments like ayahuasca, iboga, and peyote. In Gabon, Africa, iboga (tabernanthe iboga) has been declared a national treasure and is used in rites of the Bwiti religion. The active ingredient, ibogaine, is proposed as a treatment of opioid withdrawal and various substance use disorders. In countries where alcohol and tobacco are legal, certain measures are frequently undertaken to discourage use of these drugs. For example, packages of alcohol and tobacco sometimes communicate warnings directed towards the consumer, communicating the potential risks of partaking in the use of the substance. These drugs also frequently have special "sin taxes" associated with the purchase thereof, in order to recoup the losses associated with public funding for the health problems the use causes in long-term users. Restrictions on advertising also exist in many countries, and often a state holds a monopoly on manufacture, distribution, marketing, and/or the sale of these drugs. In the United States, there is considerable legal debate about the impact these laws have had on Americans' civil rights. Critics claim that the War on Drugs has lowered the evidentiary burden required for a legal search of a suspect's dwelling or vehicle, or to intercept a suspect's communications. However, many of the searches that result in drug arrests are often "commissions" to search a person or the person's property. People who consent to a search, knowing full well that they possess contraband, generally consent because they are ignorant of the fact that they have the right to decline permission to search.