Law Enforcement Officers Safety Act says police can carry anywhere not federally prohibited, however, the NFL can refuse entry to anyone they want as a Private entity.
May want to read the law again, it does not say that and it specifically exempts itself from private property:
‘‘(b) This section shall not be construed to supersede or limit the laws of any State that—
‘‘(1) permit private persons or entities to prohibit or restricts the possession of concealed firearms on their property;