Montgomerie appeared destined for qualifying until he birdied the last hole and closed with a 6-under 66 in the BMW PGA Championship at Wentworth in England, moving him from 37th place to a tie for 11th. When Kirk Triplett failed to finish second on the PGA Tour, that gave Montgomerie just enough points to reach No. 50.
But the rules dispute likely will follow him to Pinehurst in North Carolina in two weeks.
When play was suspended by rain at the Indonesian Open in March, Montgomerie failed to mark his ball in a bunker, and it was not there when the round resumed. He replaced his ball, although video later showed he put it in the wrong spot. Montgomerie wound up in a tie for fourth.
Without that result, he would not have been No. 50 on Monday, the cutoff for being exempt for the U.S. Open.
The European tour declined to penalize him, although when Montgomerie had a chance to review the tape, he felt it was an incorrect drop and donated his prize money to a tsunami relief fund. The tour's tournament committee, composed of players, two weeks ago said it was not satisfied with Montgomerie's failure to mark his ball.
On Sunday, Gary Evans said 98 percent of the players were concerned about the ruling, and that 'there has been smoke around Monty before.'
Eleven other players also earned exemptions Monday to the U.S. Open.
Justin Leonard, who won the St. Jude Classic in Memphis, Tenn., qualified by finishing in the top 10 on the PGA Tour money list through the first five months of this year, and for being in the top 50.
Others who made it by being in the top 50 were Luke Donald, Ryder Cup captain Tom Lehman, Thomas Bjorn, Peter Lonard, Shigeki Maruyama, Craig Parry, Rod Pampling, Fred Couples, Paul McGinley and Charles Howell III.
Sectional qualifying for the U.S. Open begins next week. The U.S. Open will be held June 16-19 at Pinehurst No. 2.