The United States Golf Association's position concerning distance finders is stated in Rule 14-3. In general, it is a breach of 14-3 for a player to use any artificial device or unusual equipment for "the gauging or measuring distance or conditions which might affect his play." Confusion arose over the words "distance or conditions," and in 2006 the USGA clarified 14-3 to spell out whether rangefinders and other distance finders complied with USGA rules.
The USGA states that local rules may be adopted to make distance finding devices legal. However, it distinguishes distance finders from devices that assist in determining other conditions that might affect play, such as wind speed and direction or the slopes of the terrain. It is OK to turn in a score for handicapping purposes when you use a distance finder during a round.
Why did the USGA decide that distance finders — but not devices that assist in determining other conditions — may be locally legalized? As USGA senior technical director Dick Rugge explained in 2006, "Distance information is available to players in many forms," such as stakes and metal plates on the course signifying distance and elaborate yardage books containing not only the distance to the green but to various other key locations such as hazards and bunkers. However, players don't routinely have access to factors such as wind direction and speed, so devices that measure conditions other than distance are not permitted. The USGA also recognized that distance finders can speed up the pace of play.
Range finders and their kin — laser finders and GPS devices — are permitted for practice purposes on the pro tours but not in competition. The pros use yardage books containing precise measurements of distances from various locations on each hole. Some yardage books are prepared by professional companies and then augmented by caddies. Sometimes caddies themselves walk the course and prepare the yardage books, and they are allowed use distance finders to do so.
The USGA's explanation of Rule 14-3 allows players to share a distance finder with others, so everyone in your group can use a single device, assuming the owner of the distance finder is accommodating. If you are contemplating purchasing any of the types of distance finders, check to see if the device measures anything other than distance. If so, it might be nonconforming and you wouldn't be able to use it, even if local rules allow distance finding devices.