3.3. Sources of Criminal Law: Federal and State Constitutions 
LORE RUTZ-BURRI 
Where do you look to see if something you want to do violates some criminal law? The answer is “in 
many places.” Criminal law originates from many sources. Some criminal law is the result of constitutional 
conventions, so you would need to review federal and state constitutions. Other criminal laws result from the 
legislative or initiative process, so you will need to review state statutes or congressional acts. Other criminal 
law results from the work of administrative agencies, so you need to review state and federal administrative 
rules. Other criminal law, called case law, originates from appellate court opinions written by judges. These 
court opinions, called “decisions”, are published in both official and unofficial reporters, but thanks to the 
Internet, they are now easy to find if you know the parties’ names. Much of our criminal law descended 
from the English common law. This law developed over time, through custom and tradition, and it is a bit 
more difficult to locate, but it is mentioned in treatises and legal “hornbooks” (like legal encyclopedias) and 
is often referred to in case decisions. 
The Federal Constitution—The Constitution of the United States 
Although the United States Constitution recognizes only three crimes (counterfeiting, piracy, and 
treason), it nevertheless plays a significant role in the American criminal justice system. Most importantly, 
the Constitution establishes limits on certain types of legislation or substantive law, and it provides significant 
procedural constraints on the government when it seeks to prosecute individuals for crimes. The 
Constitution also establishes federalism (the relationship between the federal government and state 
governments), requires the separation of powers between the three branches of government (the judicial 
branch, the legislative branch, and the executive branch), and limits Congress’s authority  to pass laws not 
directly related to either its enumerated powers (listed in the Constitution) or implied powers (inferred 
because they intertwined with the enumerated powers). 
Constitutional Limitations on Criminal Law and Procedure 
The drafters of the federal Constitution were so concerned about two historic cases of abuse by English 
Parliament (ex post facto laws and bills of attainder) that they prohibited Congress from passing these types 
of laws in the original body of the Constitution. (See, Article I Section 9 of the Constitution.) Ex post facto 
laws are laws that are retroactively applied, or punishments retroactively increased, or changes in the amount 
and types of evidence that is required of the government in order to successfully prosecute an individual. 
Bills of attainders are laws that are directed at named individual or group of individuals and has the effect 
of declaring them guilty without a trial. 
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