They typically file in the United States Court for the District of Delaware, a federal court located in Delaware. Delaware law plays a significant part in these cases even though they’re in Fed court. Corporate charters, filings, fiduciary duties, property rights, choice of laws, etc etc etc are all determined by Delaware law and used in the federal court.

Federal Bankruptcy Law provides the procedural framework.

So, Delaware law does in fact have nearly everything to do with it.