Violating a scientific law sounds like something that should be impossible. But the thermodynamic law stating that entropy hardly ever decreases in a closed system is a statistical one. A “violation” of that law such that in a single example entropy does significantly decrease is not impossible, but simply very rare. If the evolution on our planet should turn out to be an example of a (historic) process that has violated the second law of thermodynamics, this would make it a very rare and unusual event, no more, no less. Whether or not that is a problem for the theory of evolution depends on a couple of other considerations.
The most crucial of these considerations is the so-called anthropic bias. We (the human species) can only observe those environments (planets) where evolution has already been successful. All the other planets that stayed bleak and lifeless are observed by nobody, until some species maybe start colonizing space. At this point the fact that our evolution was successful (ex post) tells us nothing about the initial chance of evolution becoming successful when is started (a priori). Had evolution been unsuccessful on earth, but successful on another planet far away, we would just sit out there instead, wondering why we are there. Where it is exactly that evolution will become successful in the end doesn’t matter.
This is similar to a lottery where only one person in a large number of millions will win. It is extremely unlikely that it will be me to win that lottery next. But somewhere someone wins a lottery almost every day. So someone winning a lottery is not unlikely at all, but me winning a lottery is. Evolution may be similar to winning a lottery. Still there is one important difference between evolution and a lottery. While I can observe not only the winner of a lottery (say from reading a newspaper) but also myself and many other people not winning that lottery, I can only observe evolution in those cases where it has already been successful in the first place.
So observing evolution in one single case, namely our case on earth, doesn’t as such tell us anything about how likely it was before it started. Our evolution could well have been a very rare exception to the laws of statistical physics. There is no problem with that so far.
The most dramatic consequence would be that we would expect only very few other planets with intelligent live in the universe. This would at least solve the fermi paradox, asking why we haven’t met any aliens yet although they should be rather common with evolution assumed to be a common process too.