It's actuslly a bit trickier for them than that. Cannabis isn't constitutionally banned, only by a piece of legislation.

They could hold an ordinary referendum, which involves a majority of the Seanad and 1/3 of the Dail petitioning Miggeldy, and him deciding its of national importance.

However given the Government have a majority on the Seanad and an ordinary referendum has never been used before I doubt they want to do that.

Citizens assembly completed with recommendations, followed by a GE with drugs policy being fairly central with change to follow depending on the parties elected is the most likely path I think.