Impeachment is not based on a trial with breaking the laws of the United States, but based on crimes the House of Reps have created in their preparation to impeach. After the House has charged impeachment the case goes to the Senate for trial.
crimes
The grounds for impeachment are:
Treason
Bribery
Other High Crimes and Misdemeanors
The first two are pretty straight forward but High Crimes and Misdemeanor is rather strange phrase that confuses people. Many people believe the phrase means criminal felonies and misdemeanors but that's incorrect.
The founders felt that public officials had to be held to higher standards than the general public thus they selected the well know phrase, High Crimes and Misdemeanor that includes all manner of misconduct as the third reason for impeachment. It has been the common reason for impeachment.
There is no complete list of what comprises High Crimes and Misdemeanors. It includes but is not limited to the following which have been used in impeachments:
Misappropriating government funds
Appointing unfit subordinates
Failure to supervise subordinates
Drunkenness
Violation of Oath of Office
Failure to pay taxes
Not spending money allocated by Congress
Promoting themselves ahead of more deserving candidates
Threatening a grand jury
Disobeying an order from Congress
Arresting a man to keep him from running for Office
Losing a ship by neglecting to moor it
Granting warrants without cause
Essentially any federal or state law
Some of these charges were crimes. Others were not. The one common denominator in all these accusations was that the official had somehow abused the power of his office and was unfit to serve. In other words, they were guilty of bad conduct which fulfilled the founders desire to hold public officials to a much higher standard that the public.
High Crimes and Misdemeanors - Constitutional Rights Foundation