The day after the Reichstag Fire the Reichstag Fire Decree was issued which
nullified many of the key civil liberties of German citizens. With the Nazis in powerful positions in the German government, the decree was used as the legal basis for the imprisonment of anyone considered to be opponents of the Nazis, and to suppress publications not considered "friendly" to the Nazi cause.
A little hard to believe that it only took the Nazis ONE DAY to come up with the decree which
consisted of six articles. Article 1 indefinitely suspended most of the civil liberties set forth in the Weimar Constitution, including habeas corpus, inviolability of residence, secrecy of the post and telephone, freedom of expression and of the press, the right to public assembly, and the right of free association, as well as the protection of property and the home. Articles 2 and 3 allowed the Reich government to assume powers normally reserved for the federal states. Articles 4 and 5 established draconian penalties for certain offenses, including the death penalty for arson to public buildings. Article 6 simply stated that the decree took effect on the day of its proclamation.
More likely they had it all planned out and ready to go before they started the fire.