Don't be too excited about that title up there. The drugs were made legal for pretty much only one day, and that day was yesterday. In what was a spectacular legal failure for Ireland they accidentally made more than 100 drugs illegal by sort of deciding that an add on of the Misuse of Drugs Act introduced in 1977 was unconstitutional.
The amendment never officially passed parliament and was introduced anyway, meaning it was technically an illegal law. Because the amendment was thrown out, the entire act was meaning that anything banned under it became legal again. This didn't include really hard drugs like cocaine, but did include a number of legal highs and legitimate drugs such as ketamine. There were some emergency laws that were supposedly brought in in time before an official law could be made and approved today.
Remember kids; drugs are bad mkay
It was brought about when someone was arrested a few years ago and his lawyer noticed the amendment that made the drug he was caught for technically unconstitutional. Sometimes people we need to come together and accept that lawyers are a force for good. If it wasn't for lawyers we wouldn't have people accidentally making drugs legal.