Lawful, legal, legitimate, licit mean permitted, sanctioned, or recognized by law or the law.
Lawful differs from the others in implying a reference to various sorts of law (as divine law, natural law, or the law of the land, or as civil law, common law, or canon law). Consequently, the term often comes close in meaning to allowable or permissible or sometimes to rightful or proper.
Legal implies a reference to the law as it appears on the statute books or is administered in the courts; thus, the lawful heir is also the legal heir; the lawful owner of a piece of property is one whose legal right to it is certain; a moneylender is entitled only to legal interest on his loans.
Legal is used more often in the sense of sanctioned by law, or in conformity with the law, or not contrary to the law, than in the sense of allowable by the terms of the law.
Legitimate, which basically applies to a child born of legally married parents, also has been used to describe the person who has legal title (as to a throne, an inheritance, or a property). The word may also imply not merely recognition by law but recognition or acceptance by custom, tradition, or the proper authorities or logical admissibility.
Licit usually implies strict conformity to the provisions of the law respecting the way in which something should be performed or carried on; the term therefore is used especially of what is regulated by law; thus, a licit marriage, from the point of view of canon law, is one in which all prerequisites and all conditions attached to the performance of the ceremony have been attended to; licit liquor traffic is such traffic as obeys strictly the terms of the law; since dealings in the stock market have come under the control of the government, many deals once regarded as lawful are no longer licit.