Examples

The following reasonings are unestablished with respect to Paksha

'Sea cat has four legs, because it is a cat, like the terrestrial cat.'

The Paksha is 'Sea cat'. But there is nothing called 'sea cat'. Hence the Paksha is unestablished.

'American Elephant has tusk, because it is an elephant, like the Indian elephant'

In the above argument, the Paksha is American elephant, which doesn't exist. (By American elephant, we don't mean the elephants in American zoos, which are brought from India or Africa)