Yes, they are legal as long as they are used for legitimate purposes.
Professional Coursework Writing Helpers operates within the boundaries of academic integrity. They assist students in different areas, but they also advise them to use them wisely, not to be too dependent on them. Because over-reliance on them will affect your long-term learning. Such as you can use them to improve your research skills or writing skills. By taking their professionally written assignments, you get to know how to present and structure your ideas concisely. But it also varies from institution to institution. If you submit someone else's work, then it will be considered cheating.