To answer the question, to deliberately and continuously behave as if a rule did not exist, and to do as one pleases, is to flout the rule.
Anyone flouting the rule prohibiting installations of X will be subject to disciplinary action.
Flouting is more than forgetting, and more than defying a rule just one time. For instance, if you carefully drive through a red light in a quiet town at 3 in the morning, you aren't flouting the rules of traffic.
X only needs to be removed once. Not removing it isn't something that one can do repeatedly; one cannot be a repeat offender in neglecting to do a one-time action. But, of course, one can procrastinate in performing it, and one can repeatedly ignore requests to do it.
It is very difficult to prove that someone is defying the rule, or simply neglecting to perform the removal.
The way to deal with this is to set an initial deadline, and then a second deadline. The second memo makes it clear that installations of X found after the second deadline will be assume do to cases of defiance of the rules, rather than forgetfulness, and subject to disciplinary action.
Even with a second deadline, offenders can still invoke plausible deniability, such as:
- I was not aware X was on this computer; the machine had a prior user who must have put it there.
- I ran the uninstaller and it seemed to work; gee how come it's still there? I'm shocked and outraged.
- I recently lost some files and did a bunch of restoring from backup; X must have been accidentally restored. I'm so sorry about that!
- I don't use X and never installed it; someone planted it on my computer to get me in hot water.
- The famous excuse: "I didn't get the memo."
If you want to punish only intents, and not actions or neglects, you will have a hard time.
Moreover, if you send the message that only willfull defiance is subject to discipline, you're tacitly saying that it's actually okay for X to be installed, if it's only due to innocent neglect.
In fact if X is harmful, everyone must remove it, no excuses. Those neglecting to to so should be disciplined for the offense of neglecting to perform a required work duty.