Just tap may not work, unless you mean use a legal stroke.
As explained in the applied ruling section:
“It is common for a player to want to end their inning without disturbing the lay of the
table. However, the only way to end your inning without violating Rule 1-40-b is to
attempt a legal stroke. Any other action, including refusing to shoot, is a violation of
Rule 1-40-b.”
In most cases you can get the same result by just shooting away from the balls, but I can think of instances where the CB is trapped and trying any legal stroke will open up the balls. I understand why the CSI rules call for a warning in first instance but in some cases I think the right result would be a loss of game without warning.