1. The main reason civil cases are removed from state to federal court is that while filed in state court, perhaps in good faith; it is discovered that one party, usually the defendant has moved to another state. Now you have a case which if other requirements are met 1.
Deadlines. Once a case is served, the defendant has 30 days to remove it to federal court. If a case is not initially removable, but becomes removable later—due to amendment, joinder, or otherwise—this typically triggers the 30-day deadline from the date of the operative event.
A defendant or defendants desiring to remove any civil action from a State court shall file in the district court of the United States for the district and division within which such action is pending a notice of removal signed pursuant to Rule 11 of the Federal Rules of Civil Procedure and containing a short and plain ...
The thirty-day time limits are not triggered and do not restrict a defendant's right to remove a civil action to federal court in cases where no such pleading or “paper” is received by the defendant and the defendant discovers, based on its own investigation, that the case is removable.