A more thorough explanation:

Bad, adjective. Not valid or legally unsound.

• The service of process was bad because it was not delivered correctly.
• The law was declared bad by the court because it violated the constitution.

These examples illustrate that something can be considered bad if it is not legally valid or sound. In the first example, the service of process was not delivered correctly, which means it was not legally valid. In the second example, the law violated the constitution, which means it was not legally sound.