Misuse of Drugs Act (Singapore)

The Misuse of Drugs Act is a drug control law in Singapore classifying substances into three categories, Classes A, B, and C. Section 44 provides that "The Minister may, by an order published in the Gazette" add, remove, or transfer drugs among the classes.
The law creates a presumption of trafficking for certain threshold amounts, e.g. 30 grams of cannabis. It also creates a presumption that a person possesses drugs if he possesses the keys to a premises containing the drugs, and that "Any person found in or escaping from any place or premises which is proved or presumed to be used for the purpose of smoking or administering a controlled drug shall, until the contrary is proved, be presumed to have been smoking or administering a controlled drug in that place or premises." Thus, one runs the risk of arrest for drug use by simply being in the company of drug users. The law also allows officers to search premises and individuals, without a search warrant, if he "reasonably suspects that there is to be found a controlled drug or article liable to seizure". 
Moreover, Section 31 allows officers to demand urinalysis of suspected drug offenders while section 8A prohibits any citizen or permanent resident of Singapore to use any prohibited drug outside of the country, and if found guilty to be punished as if they committed that act within the country.
Thresholds.
Section 17 of the Misuse of Drugs Act lists the amount of controlled drugs beyond which, the person who carries them shall be presumed to possess them for the purpose of drug trafficking unless proven otherwise:
The possession, consumption, manufacturing, import, export, or trafficking of these and other controlled drugs in "any" amount are illegal. Persons caught with less than the Mandatory Death Penalty amounts of these controlled substances face penalties ranging from caning (up to 24 strokes) to life in prison. Pursuant to a law change in 2009, cannabis (marijuana) and marijuana mixtures (diluted with other substances) are treated the same under Singapore law—the presumed "intent" is trafficking. 
Schedule I – Controlled Drugs.
Class A – Part I.
Some examples include:
Schedule II – Controlled Drugs.
Class B – Part II.
Some examples include:
Class C – Part III.
Some examples include:
Part IV.
For the purposes of this Paragraph:
Schedule III.
These are classified as controlled equipment, materials or substances useful for manufacturing controlled drugs.