There are two ways to challenge FCC decisions. There is the upfront approach where a business whose operations are harmed by an FCC decision sues to block the decision. Then there is the approach where said business announces their non-compliance and dares the FCC to sue them. The FCC does not have criminal charging authority, so it has to rely on courts to enforce compliance. See the Federal Communications Commission v. AT&T case that just wrapped up at the Supreme Court.