While President Donald Trump mulls his rumored plan to withdraw from the Paris Agreement on climate change, others are apparently considering their own exit ― from Trump.

Among them is Elon Musk, the billionaire founder of SpaceX, Tesla and a growing number of other startups.

Musk said Wednesday that if Trump pulls the U.S. out of the landmark international accord on combating climate change, he’ll have no option but to resign from his role on Trump’s business advisory council.