How you become a condemnation lawyer might more accurately be thought of as how you become an eminent domain lawyer, and depends largely on where you want to practice law. In most parts of the world, practicing condemnation law does not require special certification or licensing beyond being a lawyer able to practice in the relevant jurisdiction. Legitimately calling oneself a condemnation lawyer will, however, probably require special focus, education, and training in the areas of constitutional law, eminent domain and condemnation.
Condemnation is a specific aspect of the law of eminent domain. Eminent domain is sometimes called compulsory purchase, compulsory acquisition, or appropriation in countries other than the United States (US). It is the law under which a government may, without permission, take possession of or an interest in a citizen's private property. Usually, such takings must serve some public utility, and must normally be compensated at fair market value. The term "condemnation" in this context refers to the formal act of transferring property to the government. Generally, any lawyer may deal with a condemnation or eminent domain case.
The process of becoming a lawyer varies widely from country to country. In most places, it begins with some form of specialized schooling — in the US, this usually means attending two to four years of postgraduate education, which is typically law school, to acquire a Juris Doctor (JD) degree. The US is one of the only nations where a certified legal education requires a postgraduate degree. Many countries allow some or all of one's legal education to be obtained as part of an undergraduate education. In some countries, and in parts of the US, specialized vocational, internship, or on-the-job training experiences can take the place of a formal legal education.
Usually, the next step in becoming a lawyer is an exam, which is often referred to as the Bar Exam or The Bar. People who pass this exam must generally join some sort of professional association. In the US, certification to practice law operates on a state-by-state basis, whereas many nations license lawyers on a national level. It is highly important to find specific information about certification for the state or country in which you wish to practice law.
In the US and Canada in particular, many condemnation cases involve the federal government, and therefore the federal court system. If you desire to become a condemnation lawyer in these or similar countries, you should probably be able to practice in the federal courts. For the most part, any lawyer can do so simply by joining the appropriate bar association. In the US, that typically means the American Bar Association (ABA).
Since any lawyer can work on condemnation cases, what sets a condemnation lawyer apart from other lawyers is mostly education and experience. If you want to become a condemnation lawyer specifically, you typically should focus on constitutional law and/or the law of eminent domain while in law school. It may also be advantageous to seek an advanced Master of Laws (LL.M.) degree in constitutional law or eminent domain.
It is also quite common for law students and new lawyers to intern, volunteer, or accept first jobs with more experienced attorneys or firms. If you want to become a condemnation lawyer, finding a mentor in the field can be invaluable. Most law schools and many professional associations can and will help novices make contact with suitable mentors.