The Indian government maintains Bylakuppe as a restricted area and one must obtain a Protected Area Permit (PAP) from the Ministry of Home Affairs in New Delhi to remain in Bylakuppe. This requirement has always been there but recently the Indian government has been enforcing it with more vigour.
In short, without a PAP foreign nationals can only visit during the day but cannot stay in Bylakuppe overnight.
It is worth noting that it can take up to 3 months to obtain a PAP and together with your completed and signed form you’ll also need to send 2 recent passport size photos and a photocopy of your passport.
You can download a PAP form here in MS-Word format or here as PDF