This is almost certainly a waste of my time but you're throwing sh*t out there and hoping people buy it soo..
Cops don't just work for local governments; there are local police departments and there are state police departments. Stop making sh*t up.
Cops determine what to charge you with (e.g. speeding & reckless driving v. just speeding; drunk in public & underage possession v. underage possession.) The fine you get depends on what they charge you for.
You have all sorts of concepts mixed up. You start out talking about how "cops work for local governments" and then shift over to "separation of powers" and say that is only at the federal level? Although you basically just contradicted yourself so I don't really need to embarrass you further, but here is some useful knowledge so you don't come off looking like a fool to the world again. Separation of powers technically applies to both state and federal government. The founders created a "federalist" system to ensure that neither state nor federal governments accumulated too much power. Ideally the system is supposed to allow both states to check the power of federal government and the federal government to check the power of the states. The system additionally adds a "separation of powers" aspect, where governments are divided into three branches (legislative, executive, judicial) at both state & federal levels, creating a system of checks and balances on each level of government.
Courts don't technically levy fines, they determine whether you are guilty/not guilty (criminal) or find for plaintiff/defendant (civil). Fines are determined by legislators, either specifically or recommended sentencing guidelines (varying by state). Law enforcement officials enforce the law (you got this one, good job!) and determine what the charge(s) is/are that you will be tried for at a hearing. If you rub a cop the wrong way, he can "throw the book at you." (Ever heard that saying?)
Legislatures are not the only ones who write/make laws. Legislation can pass both chambers, but still has to be "presented" to the Executive to be signed into law. Furthermore, executive agencies (e.g. EPA) and independent administrative agencies (e.g. SEC, FTC, FCC) are now able to make/enforce/interpret laws.
Go ahead and read my post again, because you obviously didn't read/understand it. Unlaw detention is obviously possible and happens, but not when you break a law. If you exceed the speed limit by even 1 mph, technically you are breaking a speed limit law. If you break a law, it isn't "unlawful" to pull you over while writing you a ticket & checking your background/record.
At the end you mention the Bill of Rights, while again, talking about the power of "local government cops." Not even wasting my time explaining this one...