FT: Telegram Founder Pavel Durov May Be Banned from Leaving France If Charged

"Investigators must consider they can obtain more information for the investigation or simply put pressure on him" by extending his custody, said a Paris-based lawyer with close knowledge of the process. 

If Durov is charged "it will be interesting to see what measures a judge imposes, as he lives abroad", the person continued. These could include house arrest or a ban on leaving the country.