An action by a federal agency can be constitutionally challenged as being outside of the scope or powers granted to that agency by congress. The constitutional challenge thus would be that the agency is operating outside of the checks and balances system the constitution lays out.
Congress has in the past and can today authorize agencies to do things like collect data on US citizens for national security purposes or public safety purposes.
What you describe is a statutory challenge. A constitutional challenge would be that the statute authorizing the conduct went beyond the enumerated powers in the Constitution, or that the conduct went beyond the President's inherent Article II authorities, or that it violated rights protected by the Bill of Rights.
That someone is violating checks and balances isn't really a cause of action; you would be more specific in your case.
Congress has in the past and can today authorize agencies to do things like collect data on US citizens for national security purposes or public safety purposes.