A foreign legal opinion (or foreign law opinion) is an opinion of a law firm issued in cross-border commercial transactions certifying the effectiveness of the transaction under the applicable foreign law. Foreign legal opinions have become highly standardised over time, and most foreign legal opinions follow a fairly regimented format. The issuance of such opinions has become something of a sub-legal specialisation in itself, and books and articles are written on the subject of foreign legal opinions. A number of organisations issue template format opinions to indicate issues which are intended to be covered by such opinions, or standard form checklists for contents.