My apologies, Spaniel, I was away for awhile.
Under the circumstances you have described and in the absence of any specific restriction in the community by-laws, there would appear to be no reason that this person cannot walk anywhere in the common area grounds of the community.
However, there are two considerations that may be of some assistance to you. Regardless of the common area status, the patios or decks would be considered private and he would be trespassing if he went onto either of those. Trespass is both a civil wrong and a misdemeanor
crime under Minnesota Criminal Code section 609.605. You can see this code section at:https://www.revisor.leg.state.mn.us/statutes/?id=609.605
Furthermore, if he is actually looking in the windows, that would be considered interference with privacy ("peeping Tom"), which is also a crime under Minnesota Criminal Code section 609.746. You can see this code section at:https://www.revisor.leg.state.mn.us/statutes/?id=609.746
Therefore, if he does either of these things, you can file a complaint with the local police department.
You might also consider asking the association board to modify the by-laws to clarify the privacy rights of the community's residents with respect to the property immediately appurtenant to each unit, including the decks and patios.
Thanks for asking your question here on JustAnswer. If you have any other questions, please let me know.