If you raise your arms to inhibit the receiver’s play on the ball, without turning to play the ball yourself, it’s pass interference. Besides, if your back is to the ball you have zero chance of intercepting.
Faceguarding is not a foul. I don’t think it ever has been at the NCAA level, though it was in NFHS some years ago.I think face guarding is PI, but if you make no physical contact with the receiver and raise your arms as the ball gets there I don't think that gets called
From the 2019 NCAA Football Approved Rulings 7-3-8:
“I. B33, defending against a legal forward pass beyond the neutral zone, has his back to the ball and is waving his arms in the face of eligible A88, but does not make contact. RULING: No foul. There is no foul for defensive pass interference if there is no contact.”
Excerpt From
2019 NCAA Football Rules / Interpretations
National Collegiate Athletic Association
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