People enter the law for diverse reasons: a desire to see justice done, the daily intellectual challenge, and the temptation of sky-high salaries for top performers are all valid reasons. Whatever your motives, if you have an excellent memory, an analytical mind, a great work ethic, and good verbal and written communication skills, your talents will not be wasted in a legal career.
You should know, however, that the daily grind of a lawyer is nothing like what is shown on TV. To be slightly flippant, the chief responsibility for worldwide deforestation is probably a tie between the palm oil industry and the legal profession. Lawyers handle an immense amount of paperwork and typically spend long hours at the office. If you're not prepared for this aspect of the job, a different career path will probably suit you much better.
The normal route to becoming a lawyer in the United States is to first get a bachelor's degree. Virtually any four-year degree will do, but most aspiring lawyers choose a field that hones the research and critical thinking abilities they will need in their professional life. Philosophy, history, political science, and of course undergraduate criminal law are all popular choices. A person who hopes to specialize in a particular kind of law will generally take a related major, for example ecology for environmental law or engineering for patent law.
After or shortly before graduating, you're entitled to take the notorious LSAT for admission to law school. This is more of an aptitude test than one verifying your knowledge of specific subjects. If you do well, you'll be admitted to one or more law schools to earn your Juris Doctor degree, which generally takes 3 years to complete. You can then take the bar exam in your state and, assuming you pass, begin to practice law.
Can you earn a law degree in Europe and return to work in the United States? The short answer, which happens to be a phrase lawyers have to use a lot, is "it depends". Specifically, lawyers are generally licensed at the state level. Each state's Bar Association has different rules on who may take their tests.
Some require you to complete a certain number and types of courses at an American university, others don't really recognize foreign credentials, and a few don't even need you to have a formal degree of any sort (though passing the bar without one is of course rare). These rules are listed on the website of the Bar Association of whichever state you hope to practice in.
In short, being admitted to the bar with a European degree is significantly more difficult than with an American LL.M or J.D. The reason many students continue to earn their law degrees in Europe so comes down to cost (and perhaps the adventure of living in a foreign country). The average cost of tuition for a law degree in Germany, for instance, is only about €10,000.
