Is it a foul to hit “into” a cue ball frozen to an object ball?
When the cue ball is frozen to the object ball, you are allowed to hit into the cue ball toward the frozen ball with a normal stroke. In fact there are aiming systems devised just for this type of shot. High-speed video footage clearly shows that hitting into a CB frozen to an OB, with a normal stroke, results in a non-pushing, clean hit, just like any other legal shot. Examples can be found in HSV A.96 and HSV A.97. These shots might “feel” like “push” shots, but they are not. Examples of true push shots can be found on the push shot foul resource page.
Now, if there is a miscue during a frozen CB shot, it could be ruled a foul if there are obviously multiple hits or if the miscue is intentional. HSV 7.5 is an example that is tough to call, even with high-speed video.
For many example calls along with explanations, see the following videos:
How do you aim frozen-ball carom shots (e.g., a frozen carom/billiard shot or a frozen spot shot in one-pocket)?