"Legal highs" are legal no more, with the Psychoactive Substances Act 2016 having coming into force on Thursday.
But what does it mean, what does it cover, and will anyone go to jail?
What are "legal highs"?
"Legal highs" are substances that have similar effects to banned drugs, such as cocaine or cannabis.
"Legal highs" carry health risks, as they often contain ingredients which have never been used in drugs for human consumption before.
If they can be dangerous, why have they been legal?
"Legal highs" contain new substances which are not yet controlled by the Misuse of Drugs Act 1971. Often the ingredients are also changed to overcome any bans.
"Legal highs" cannot be sold for human consumption. To get round this, they are often sold as plant food, incense, or salts.
So what's happening and when?
From Thursday, "legal highs" are to become illegal under the Psychoactive Substances Act. This means there will be a blanket ban on the production, distribution, sale and supply of legal highs which are intended for human consumption.
What does the Act mean by "psychoactive"?
For the purposes of this Act a substance produces a psychoactive effect in a person if, by stimulating or depressing the person’s central nervous system, it affects the person’s mental functioning or emotional state.
What about alcohol and nicotine?
The new law excludes alcohol, nicotine, caffeine, and medical products.
Poppers (alkyl nitrates) are not covered by the ban as the Advisory Council on the Misuse of Drugs (ACMD), said they produced "peripheral effects" on the brain, and so would not be included.
Didn't this happen a while ago?
The Psychoactive Substances Act was meant to come into force on April 6, but legal deadlines were missed and there were concerns over whether the blanket ban was enforceable.
Critics were also worried that the use of word "psychoactive" was not clear enough in what it covered. It could have meant that herbal medicines were covered by the ban.
Following advice from the ACMD, the legislation was rewritten.
Will you be jailed under the new law?
Offenders can face up to seven years in jail.
The Act will also enable police to shut down "headshops" (stores from which "legal highs" and drugs paraphernalia can be bought) and online dealers. They can also seize and destroy psychoactive substances, as well as search people, premises, and vehicles.
But will it work?
The prospect of prosecution and a jail term may put some people off.
However, new "legal highs" are being created all the time, meaning that it may be hard to control them.
There are also fears that the sale of "legal highs" could move to the dark web.