The Justice Department gave California high schools one week to confirm that they will comply with the Trump administration’s stance on transgender athletes as the government takes aim at the state’s regulations allowing students to compete on the basis of gender identity.

AB Hernandez, a transgender athlete, has stirred controversy and drawn national attention over competing in a girls track and field championship. NBC News' David Noriega explains how Hernandez was able to compete under a new California policy.

A Justice Department letter threatened action over California’s policy allowing trans athletes in girls’ sports. President Donald Trump promised “large scale fines.”