The United Nations (UN) offers a wide variety of work for lawyers in many different countries. This can include legal advisors for the UN in Geneva or New York; advising governments on judicial reform; training and advising judiciaries on legal issues, long-term education and legislative reform; advising on the implementation of legal aid structures; working in conflict environments; courtroom prosecutions of human rights violations etc.
The UN Careers Human website (https://careers.un.org/lbw/Home.aspx) lists job vacancies and can be searched by job type/network eg "legal". Salaries for professional staff are set by reference to the highest-paying national civil service - that being the USA.