Casey abandoned his membership this past year to focus solely on the PGA Tour, and his game experienced a turnaround as a result. Casey's season ended with a Tour Championship appearance and was highlighted by playoff losses at both the Northern Trust Open and Travelers Championship. After beginning the year ranked No. 75 in the world, Casey is up to No. 24 in the latest standings.
Casey makes his home in Arizona, and in a statement to Britain's Press Association Sport he explained that his focus will remain in the U.S.
"With my wife and young son as a priority, I have decided to concentrate on the PGA Tour which has worked well for us this past year as I have climbed back up the rankings," Casey said. "I am very sad not to have the chance to qualify for the 2016 European Ryder Cup team, but I believe this decision will help me to be the best I can be both on and off the course and is the right decision for my family."
European Tour chief executive Keith Pelley announced membership changes this week designed to make it easier for European players based in the U.S. to maintain membership. Instead of making 13 starts inclusive of majors and WGC events, players now need only to make five starts in Europe outside of the year's biggest events.
While the change spurred Russell Knox to claim membership Friday in a bid to make the team at Hazeltine, it wasn't enough to sway Casey.
"I respect Paul's decision but, as I said on Tuesday of this week, we have made it very easy for players to retain their membership of the European Tour by only having to play five out of 37 tournaments outside the majors and World Golf Championships," Pelley said. "If that is not feasible for Paul, then there is not much else we can do."
Casey played for Europe in three straight Ryder Cup teams from 2004-2008, but he was notably left off the 2010 team by captain Colin Montgomerie despite being ranked inside the top 10 in the world.
"It is obvious that representing Europe in the Ryder Cup is not on Paul's priority list, which is disappointing, but I wish him all the best in the future," said 2016 captain Darren Clarke.