It isn't unusual for a lawyer to spend a half hour trying to find the right section of a legal text to read. Most law libraries will have many of these secondary sources. Most public lending libraries will not. Once you have found your keyword in the index of a secondary source, you will be able to find the sections of the text that describe the item you are researching. You read the sections on expirations, and you may find two kinds of references.
Lawyers understand that the supreme law of the land is the Constitution.
But the Constitution rarely comes into play directly in a court case. Even if a case contains constitutional issues, there are so many court cases that have interpreted the Constitution that judges usually spend their time looking at all of those interpretations instead of at the Constitution itself. Below the Constitution are federal laws, which have supremacy over state laws. In some areas of the law, there may be no statute involved, since the law may have developed over hundreds of thousands of years by judges' decisions. But in most areas of the law, there are statutes that rule the situation.