What is this?

[MD Longhorn]

You CANNOT call obstruction on a fielder that has the ball.

Whether you can, or should, in this case use rule 10 to rule on a situation not covered in the rulebook (a situation which seems to me to be something that could easily be foreseen by the rulesmakers and thus would be in the rulebook if they wanted it to be against the rules ...) is the issue at hand.

[Dakota]

The rule book is clear that obstruction can only be called on a fielder who is not in possession of the ball (ISF excepted) who is impeding the progress of the runner.

Putting it another way, impeding the progress of the runner is in the "job description" of a defensive player with the ball.

But, does this legal impeding include grabbing, hooking, tripping, or tackling and THEN making the play on the runner?

I have a hard time with that being the situation intended to be covered by the obstruction rule, but short of using 10-1, it would seem an out is the only call supported by the book.