In America, foxes are considered to be 'protected furbearers,' or game animals in most states. Many wildlife agencies allow for the removal of foxes to protect private property, but others are stricter. For example, in West Virginia, it is illegal to trap animals without a permit or move them to another location, without prior approval. Over in Utah, red foxes are classified as protected wildlife but they can be taken year-round, with no license required. So, you must seek local advice before acting.
Note that the Sierra Nevada red fox is protected and listed as an endangered species, while the San Joaquin kit fox is federally listed as endangered and listed as threatened by California. There are other protected foxes, too, so check your state’s regulations in advance.
The best thing to do is to deter foxes. Do so by removing food sources – secure or lock garbage cans away, invest in bird feeders that don’t spill food onto the ground, protect edible crops, and promptly clear up any fallen fruits. Fish, blood, and bone fertilizer can also attract foxes, so consider switching to a plant-based product.
If a fox has already made its burrow in your backyard, wait until the cubs have left the den in late summer, before actioning the above deterrents. You can encourage the mother fox to move her cubs by making noise and walking nearby.