In your petition, clearly explain why you are being held illegally. The writ of habeas corpus primarily acts as a writ of inquiry, issued to test the reasons or grounds for restraint and detention.This Chapter explains the writ of habeas corpus and lays out the procedures you will need to follow to petition for the writ. The privilege of the writ of habeas corpus shall not be suspended except in cases of rebellion or invasion when the public safety may require it. All forms below with a "fillable icon" are documents that you can open "on-line", fill in the appropriate fields and then print on your printer. This petition, called a writ of Habeas Corpus, is filed in Federal Court (US District Court ) whether you are serving time in a federal or state prison. 251 (1947); A Study of the Illinois Supreme Court, is Univ. Chi. All Illinois Courts must accept these forms. 1 (The term "federal law" includes not only federal statutes, but also U.S. treaties and the. Fill out the illinois petition for writ of habeas corpus form for FREE!