5 plants of hemp or 15.0 grams of marijuana, 40 pieces of magic mushrooms, 5.0 grams of hashish, 5 LCD laced papers or other materials with LSD, 1.5 grams of heroin, 1.0 grams of cocaine, and 2.0 grams of methamphetamine. That is what you can have legally in your possession from January 01, 2010, in the Czech Republic; the maximum offense for such is now just an infraction.
This is the way of the Czech Republic government to decriminalize the common drug users, who had previously ended up frequently in jails and prisons. The government would rather see the dealers incarcerated; however, the experience from the past was the vice-versa case. The drug possession for own use will be taken more loosely than in the neighboring countries. The Polish police officers are, for example, afraid that the happy Polish youngsters will be using the other side of the bridge in Český Těšín for partying (the city is half in Poland and half in the Czech Republic, with the border crossing the bridge).
Therefore, the visitors of Prague will now find Prague a bit more enticing, like the Netherlands. You will not be able to buy a joint of marijuana in a “coffee shop” like, for example, in Amsterdam, but you will not have to spend time in jail just for partying in a club and having a little joint on you.
Some are now joking that the new law might have paradoxical consequences. Of course, like everything when abused. Imagine a village with 356 inhabitants, and each of them growing 5 plants of marijuana. That would be a large field behind the village. Moreover, the people of the village can jointly punish themselves for infractions at the municipal hall. Each day one of the villagers would get the public service works as punishment, and he/she will be rolling joints for the others.