I have experience in domestic law, but international law is another 'kettle of fish'. [='matter']
The 'kettle' is boiling. [=the water in the kettle is boiling]
Put the 'kettle' on (the stove) so we can have a cup of tea.
(..) If someone wants to volunteer. And if they showed some remorse. I just want some tea, Grandpa. I just need something warm. But no. The kettle whistle is missing. I'll make such a blend of herbs, that it will make your eyes pop from their sockets. Oh, Agatha! Who did this? (..)1989 Dva lidi v zoo