About as dumb as a law can be! A high percentage of vehicles sit 90+% of their ownership/life inside garages or even in A/C/climate controlled spaces. Many vehicles see well under 5,000 miles/yr. That's out of the sun, rain, salt, airborn polutants, etc and force them to buy new tires? For what reason? 40+ year old tires on street legal licensed historical or antique vehicles kept inside have NO tire rot or issues requiring replacement. Each case with tires needing replacing is very different and one bogus law doesn't relate to even half of reality.
The sun and heat compromises and rots tire compounds but most of North America averages only 25% or less of a 24 hour day with sun and then it's only on one side of the vehicle and it's tires. In the south and west, tire rot is many times the problem of the rest of North America and Maryland isn't even close to the high hot sun areas. How dumb can a legislature get?