This one is pretty simple, and mirrors the Embedded Ball Rule change in essentially flipping an often-used Local Rule into a standard Rule.
In 2018’s Rules of Golf, Rule 14-3b, Appendix 1A (section 7), and Appendix IV (section 5) cover distance-measuring devices (DMDs) as such:
- The Rule prohibits the use of DMDs during a round.
- The Appendix allows a Committee to adopt a Local Rule allowing the use of DMDs.
Virtually every tournament in which amateur golfers play have allowed DMDs during the round, so in 2019 the Rules “flip flop” here:
- DMDs are allowed under Rule 4.3 during a round.
- A Committee may adopt a Local Rule prohibiting the use of DMDs.
In other words… very little will actually change at your level, except the Committees of the events in which you play can save a little ink by not adding the Local Rule permitting the use of Distance-Measuring Devices. On the PGA Tour, the Local Rule prohibiting their use will probably just go on what is known as the “hard card.”