Ontario Premier Doug Ford has fired back at Donald Trump by putting up a giant “Lake Ontario” sign on Canada’s shoreline. The move comes after Trump signed an executive order renaming Lake Ontario “Lake America” for U.S. federal use. Ford’s bold response, “Lake Ontario. Now and Always,” adds a new twist to the growing U.S.-Canada naming and trade dispute.

Canadian Prime Minister Mark Carney and Ontario Premier Doug Ford quickly denounced Trump’s move and said Lake Ontario’s name was here to stay.

Trump’s executive order may change the name in the U.S., but Canada isn’t required to follow suit. Here’s who gets to decide and where the centuries-old name came from.