Your question makes assumptions that are not correct.
There is no reason to accept mail for an unknown addressee, by anyone.
The manager's job is to accept mail for known addressees.
Yes, it is a federal offense (violation of United States Postal Regulations) to interfere with the delivery of someone else's mail.
I know of no traffic violation that amounts to a felony offense and of no traffic violation which would fall under the jurisdictioon of the federal governmnent.
It's not a "crime" to accuse someone of opening mail if it is accompanied by proof or probable cause that they were doing it. However, it IS a violation of US Postal Regulations (a federal offense) to open mail belonging to someone other than the addressee.
It's a civil violation of federal law.
Violation of Federal law may put you in Federal prison. If it is determined to be a violation of a STATE law, it will depend on the laws of the individual state.
It is Illegal and a violation of Federal Law, to remove the catalitic converter.
A federal question case takes place when the alleged plaintiff is charged with a violation against the United States Constitution. It can also a violation against federal law or a treaty which the United States is party to.
If you are currently incarcerated you have to speak with your attorney. They can contact your PO to convince them that a federal hold is not a probation violation. If the case is dropped then most likely you will not be in violation on a federal level. Feds only care about major cases and if your violation is small they might release the hold if the attorney talks to the PO.
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Federal law.
A broadly defined as an act which violates state or federal law
It is a violation of Federal law to do so.