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Second row Willemse saw red 13 minutes from time when, trying to pull Wyn Jones away from a ruck, he grabbed the Wales prop round the back of the head.
As Jones fell backward, Willemse's fingers slid over his eye.
He was sent off by English referee Luke Pearce at the Stade de France following a video review.
Wales, however, were subsequently reduced to 13 men following two yellow cards and France came from behind to win 32-30, with full-back Brice Dulin's added-time try sealing a stunning victory that denied the Welsh a Grand Slam.
A Six Nations statement issued after a disciplinary hearing on Wednesday said Willemse accepted he had committed an act of foul play, in making contact with the eye area.
But the disciplinary committee decided there was insufficient evidence that Willemse had made contact with the eye itself.
They determined the 28-year-old South Africa-born lock "had acted recklessly and not intentionally".
As there was no evidence of injury to Jones, the committee found the offence warranted a low-end entry point of four weeks.
But they cut the suspension in half to two weeks after also taking into account his guilty plea and remorse.
Willemse, who can appeal the decision, has also been ruled out of Montpellier's European Challenge Cup tie with Glasgow and is free to play again from April 5.
France should have played its third-round tie against Scotland in Paris last month, but the match was postponed because of a Covid-19 outbreak in the French camp.
If France enjoy a four-try bonus-point victory over the Scots by a margin of at least 21 points, it will win the 2021 Six Nations title.
Anything less, and Wales will be crowned champion.