In what you might call a joint statement, Tokyo 2020 organisers Tuesday noted the need to warn countries with relaxed cannabis laws that weed isn't allowed in Japan.

"There are countries and regions around the world that have relaxed rules recently on the use of cannabis," noted Tokyo 2020 CEO Toshiro Muto.

"The use of cannabis constitutes a violation of the law in Japan and that needs to be fully communicated," he added.

Muto said the topic was raised by a member of the Tokyo 2020 executive board as something that should be transmitted to the heads of country teams when they visit Tokyo ahead of the Games.

Cannabis rules in Japan are strict, with up to five years' prison for personal use and seven years for dealing.

Cannabis is also listed as a performance-enhancing drug by the World Anti-Doping Agency.

The US anti-doping agency USADA notes on its website that marijuana could "decrease anxiety and tension, resulting in better sport performance under pressure".

"Due to the illegal nature of marijuana in most countries, the use or abuse of marijuana does not exhibit the ethics and moral judgment that upholds the spirit of sport," the body adds.

The issue hit the headlines in Japan when two Japanese snowboarders were punished after traces of marijuana were detected in their hair following a party in December 2015.

One of the athletes admitted taking the drug at a party while on tour in Colorado, where cannabis was legalised for recreational purposes in 2012, provided the user is 21 years old.

Skateboarding and surfing, two counter-culture pursuits with reputedly high rates of drug use, are among the sports that will be contested at Tokyo 2020.