Technically, yes. The same goes for other Pokemon simulators. However, it is a pointless exercise to do so, as the people who operate these sites could easily open them up at a different URL and hosted on a different server.
What the people who run the simulators are doing, while it technically violates copyright law (and many of them use official resources without permission and outside the bounds of fair use), it is difficult to prosecute due to the nature of the internet.
Looking at it long term, as I believe Nintendo and Game Freak would have done, it is better to ignore what they are doing as trying to stop them will ultimately turn out to be a waste of resources, as even if they stop the current simulators new ones will crop up.
We shall rise again to start anew. White FC: 0862-2660-4156 / 3DS FC: 2492-4470-1418 / White 2 FC: 4556-7836-2644