- some laws are enforced by a bureaucracy, the police or an executive agency which can invoke legal sanctions, fines or imprisonment after due process.
- some laws are enforced by opposing parties which can file civil suits accusing their opposition of violating a legal provision.
- some "laws" are applied by one part of a bureaucracy against the bureaucrats within it
Most laws rely on voluntary compliance; people incorporate their understanding of law and justice into their consciences and abide by it, until it becomes too inconvenient or their understanding of the situation or of law changes. That means that the bureaucracies and the civil lawsuits mostly serve as backups, at least in most "advanced" countries.
But that leaves a hole--it's difficult to enforce laws on heads of bureaucracies, the top level who set policy and who therefore supervise those who are charged with enforcing the laws.
We deal with that hole in two ways in the US:
- each agency (i.e. cabinet department) has an inspector general who's independent of the heads of the subordinate units
- each agency has Congressional committees and the GAO (which works for Congress) with oversight responsibility.
That still leaves the big hole at the top of the government: enforcing the President's compliance with laws. This Just Security article discusses a big one--the Presidentiall Records Act. The Act is part of the overall structure of rules on government records, none of which get much respect. NARA can try to enforce the rules on the agencies, but as the article discusses there's no way, outside of politics, to ensure the President follows the rules.