That is a very bold step from Ravichandran Ashwin. The BCCI doesn't permit Indian players to participate in foreign leagues if they are active. Ashwin need to "retire" from all forms of cricket before he becomes eligible to play in these competitions. And that will put the BCCI in a spot of bother. In case Ashwin has retired, how he continues to play in the Hundred? So far they have allowed players to play in the legends series, but those are mostly players who are in their mid-40s and 50s.
He did technically retire from all formats of cricket except for the IPL which he has retired from now which is why I don't think it will be a problem for him despite BCCI potentially landing in a spot of bother as you mentioned.
He is a gutsy dude who isn't afraid of taking risks which is why he probably will play in foreign leagues sooner than you think.