Trump shrank 2 national monuments by nearly 2 million acres. He can't do that to Yellowstone.

President Trump may have just dramatically slashed the size of two national monuments in Utah, but America’s 59 national parks — as well as over 270 other national park sites — cannot be unilaterally downsized by Trump or any other president. 

The legal reason is simple and inarguable:

“National parks can only be established by Congress, and everyone agrees they can only be undone, if at all, by Congress,” Holly Doremus, a natural resources law expert at University of California, Berkeley, told Mashable in an email. 

More about National Parks, National Monument, President Trump, Environmental Protection, and Ryan Zinke
Source: Mashable | Trump shrank 2 national monuments by nearly 2 million acres. He can't do that to Yellowstone.