I checked on this, there is something called a Qualified foreign investor(threshold is 50 million) who can have direct access to NSE.
For others. as I said earlier, contact IB cc to find out.
Those who want to trade Banknifty legally can still do it the way I posted.
If a trader is really good then Banknifty is the only route forward.
Many of the broker employees use it as a lottery buying hundreds of lots of calls and puts on expiry day. I've seen guys doing 40 times on swing trades, and in the current market uncertainty with covid there are going to be some massive opportunities for good traders.