What is the law for bail according to you? Bail is always permissible for any ACCUSED (note: accused, not convicted) as long as there is no risk of fleeing. "Bail is the norm, jail is the exception" is the supreme court directive for any accused.
Putting someone in jail is a form of PUNISHMENT, which in theory should only be given after somebody is found guilty through a fair trial. And that is precisely what India is doing, giving them a fair trial. If they are found guilty by the court, then they will spend the specified time in jail, and there will be no Christmas visits or journeys for vote. But before such a verdict is reached, they are undertrials, presumed innocent until proven guilty.
And since there is no flight risk (due to the assurances of the GoI), the court has to grant bail. And this is true for anybody who is not a flight risk. Kasab obviously doesn't fall into that category, of not being a flight risk.
Why was Yusuf Memon allowed bail who was sentence to life during Bombay bomb blast?
He could have fled to Pakistan as his brother did.
So he was a flight risk too.
Tiger memon is still in Pakistan.