Before you discipline an employee's behavior, take a step back and see the "why" behind it. It could surprise you.
If you are in any kind of management or supervisory position, you will undoubtedly experience a "rogue employee". The one that is usually fantastically on-point and then all of the sudden starts behaving very differently, even to a point of perceived disrespect. This is a great learning opportunity for you both. The best thing to do is to stop and take a moment to review the behavior and intent behind it. It may not be what you think.
Let's say Susan is your star employee. She gets her work done, helps others out when needed, creates opportunities for success, and then suddenly, she's all over the road and not focused. Maybe she's getting the basics of her work done, but she's really starting to annoy you and you can't figure out why. It's little things, really, but they are measurable in your mind. First you ask her questions and her response tells you, "No, that's not what I'm talking about. You misunderstood." Then the decision to mix up her work hours without consulting you first. Next comes, "Oh, I forgot to tell you but I'll be out of town Thursday and Friday next week. I've already bought my plane tickets." There can be several reasons for this behavior switch, so let's look at a few before you discipline Susan.
First, Susan may be feeling full empowered (and good for you for allowing your employees to feel empowered!), but does not understand the guidelines of such empowerment. When you give your employees the opportunity to stretch, grow and be creative in their jobs, you're giving them a level of freedom that perhaps they've never experienced. When you give them this empowerment, it comes with consequences that need to be provided and explained. Susan may be looking for your boundaries. Where is the line in the sand?
Second, Susan is trying to express herself as a top-notch, independent employee that is capable of making higher level decisions that her pay-grade offers. You often hear, "dress for the position you want," and perhaps that's what Susan is doing in her mind. Acting the position she wants or feels she deserves. Have you set up goals and rewards for her? Does she understand when she will be provided a raise or review of her performance?
Lastly, when was the last time the two of you sat down and talked? Do you know what her needs are? Perhaps the out of town visit is family related, and there are pressures and requirements she is not sharing. Rather than ask permission, she feels asking forgiveness is the lesser of the painful conversations.
There are several dynamics going on in every persons like at any given moment. So before you condemn and see behavior as a negative, investigate a little further and keep in mind that people don't want to be malicious and manipulative (well, most of them don't) but perhaps just trying to be expressive. Be sure to have your working policies and guidelines set up, expressed and very clear. If this turns out to be a true rouge employee, action must then be taken to prevent any further disruption to the team.