Law books don't come cheap, but the information they contain can go out of date quickly. You can try to sell law books that you no longer need on an auction website or to a secondhand book shop. but the huge loss that you'll take will probably make you a bit sick to your stomach. An alternative to selling law books is donating them to a library or a charity. You won't see any money from this but it will help others who are striving for a career in law.
Make a list of law books you wish to donate including the title, the writer, publisher, the year the book was published and the condition of the book. Libraries will appreciate this information so they can determine which books they wish to bring into their collection. Don't be surprised if they don't want all of your books. They may have several copies or they may have little interest in the category that your law books belong to.
Call your local library and advise them that you wish to donate your books. Discuss with them the information on your list and schedule a time to drop off the books that they are interested in.
Find an international cause to support. For example, Books For Africa says law schools in Africa have an inadequate supply of law books for their students. There are many national and international organisations that will happily accept any law books that your local library might not want. You can contact most charities via their websites to locate delivery and drop-off addresses.
If you donate books to a charity, not for profit groups or even businesses, you can request a tax deduction receipt to recoup some of the loss incurred by donating your books and not selling them.
Giving to charity will help others learn but you should know the value of the books you are discarding. In some cases a value of a book can be quite high and selling the book may present a better option for you.