What are the tax rules if an NRI becomes 'karta' of HUF?

There are no restrictions on an NRI becoming 'karta' as long as person is coparcener of HUF. For income-tax purposes, HUF is treated as resident of India unless control and management of affairs of HUF is situated abroad. Even if HUF is treated as non-resident for income-tax purposes, it is liable to pay tax on income which arises in India.