Yeah, we have a law that was imposed several years back, that says you cannot run the lake with a spotlight on continuously. Supposedly, it can "blind" an oncoming boat driver but in all the years prior to the law I've rarely (if ever) met an oncoming boat where their spotlight was of great concern to me. I just did the same thing as I would do on the road when an oncoming vehicle had their brights on .... I didn't look right at the oncoming light.
At first I had my doubts about the validity of their reasoning. I kinda thought maybe it was being pushed by the Bass guys that fished a lot of night tournaments, who were getting tired of being spotlighted to find out the banks they were fishing on. I never did dig into that theory very deeply, though, and just went with the crowd & ..... anyway, it's supposed to be "okay" to periodically turn the lights on for guidance, just not run them continuously.
The other rule that was implemented around the same time (I think) was that boats not under power at night still had to have their transom light on ... which was supposed to be a guard against another boat crashing in to you when you're fishing down a bank & the other boat (without a spotlight on) decides to come to the same spot. The transom light must be visible 360deg & at a distance of 2miles in clear weather. (what they didn't take into account was that the transom light draws bugs at head level of the person in the back seat, or that it also casts shadows towards the bank you're fishing & dampens the effect of any "black lights" being used).