A few weeks back there was rumor of a revolt by ATP 250 level tournament directors in response to the announcement that top ATP players including Rafael Nadal would be playing an exhibition event in Asia the same week that the ATP would be conducting 250 level events.
It took a couple weeks, but I finally got an answer from Austin Nunn and Kate Gordon, the Executive VP of the ATP Tour's Marketing and Communications.
The ATP Special Events Rule has been consistent since the governing body’s inception in 1990. Players are allowed to play in non-ATP events during the week of an ATP World Tour 250 tournament if it is located more than 100 miles (160km) away and not considered the same market area of the city where the ATP World Tour tournament is located.
Over the years, the ATP Board of Directors has considered various proposals to modify the Special Events Rule. However, the Tour believes that the current rule provides an appropriate balance between promoting the ATP World Tour and the investment by our tournament members, and allowing our player members -- who are independent contractors and not ATP employees -- some flexibility to play in non-ATP events throughout the year, while fulfilling their commitments to the Tour.
Bad news for ATP 250 tournaments that sometimes struggle to attract a top-10 or top-20 player in their field. I'm not sure men's professional tennis becomes "the wild west" again, but it could spell the end for some 250 events around the world.