There are some here who reject the uniformity of natural laws. They claim that we cannot know that things like radioactive decay rates or the speed of light were the same in the past.
To these people, a simple question: how do you know to stop at a red light?
Your example is poor because it relates something that you believe is intelligently designed (red lights) to something that you do not believe is intelligently designed (natural laws).
In addition, you are missing the fundamental argument. Let's say, for the sake of argument, that there is one set of uniform, unchangeable, unshakeable, unalterable natural laws that even God himself cannot vary in the slightest.
How, then, do you know that your theory T is an example of that unalterable law?
Let us consider the case of a hyper intelligent 3-month-old child. He is able to speak, to reason, and even to do advanced calculus. He is entirely self taught. One day he approaches you and says, "We have a problem."
"What's the problem?"
"The sun is dying."
"How do you know?"
"Every day is shorter than the previous one. Soon we will all be plunged into eternal darkness."
-------------------
What's the situation? The child has observed a trend and assumes that this trend will go on forever. He does not know that this is a cycle. Yes, the days will get shorter until the winter solstice after which the days will get longer.
The question, therefore, is not "How do you know that the laws vary?"
The question is, "How do you know that the rule you have postulated is one of the invariable laws and not just based on your observation of the last few hundred years of a one-billion-year-long cycle?"