Interesting ramifications to measuring legal length of Abalone. In California, you can get a ticket for using a gauge longer than 7"

"Abalone divers are required to “… carry a fixed-caliper measuring gauge capable of accurately measuring seven inches” (California Code of Regulations Title 14, section 29.15[f]) and are required to retain any legal-sized abalone they detach and add them to their bag (CCR Title 14, section 29.15[d].) It is fine to use a gauge larger than the required 7-inch gauge to measure over-sized abalone when trophy hunting. The problem occurs when a diver detaches and brings an abalone to the surface, measures it with only a 9-inch gauge, and then rejects it for being smaller than their personal target size even though the abalone may still be of the minimum legal size (seven inches or larger). This practice puts the diver in violation of the above sections and this practice is considered “high-grading.”

To avoid this kind of ticket, divers should not return any abalone before first measuring with a 7-inch gauge to be sure they are smaller than legal size. A 7-inch gauge should be in the immediate vicinity of where the diver surfaces (in hand, float tube or kayak) so that the abalone can be readily measured, and if they then turn out to be short, the diver can then return it to the same location where originally taken. The violation occurs when divers detach and then reject legal-sized abalone because they are seeking only the oversized ones."