As of the 16th, League of Legends players are now able to cross the seas and transfer between the North America and EUW or EUNE servers. This is definitely a feature that players have been waiting for for a while.
I myself would have loved this feature to be implemented sooner, but, you know what they say: better late than never!
Riot themselves are definitely aware of this and stated via the official League of Legends website:
This upgrade has been a long time coming and we’re stoked that players now have more flexibility to choose where they play!
League of Legends server transfers will cost players 2600RP, are one-way, and can be accessed via the in-game store, under the ‘Other’ tab.
Additionally, European players who joined the North American server before June 1st 2010, and weren’t able to move to the European platform when it opened, will receive a free one time transfer token.
For more detailed information on how server transfers will work, head on over to the FAQ at the official League of Legends site.