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4 U.S.C. §5
United States Code, 2011 Edition
Title 4 - FLAG AND SEAL, SEAT OF GOVERNMENT, AND THE STATES
CHAPTER 1 - THE FLAG
§5. Display and use of flag by civilians; codification of rules and customs;
“SEC. 3. RIGHT TO DISPLAY THE FLAG OF THE UNITED STATES.
“A condominium association, cooperative association, or residential real estate management association may not adopt or enforce any policy, or enter into any agreement, that would restrict or prevent a member of the association from displaying the flag of the United States on residential property within the association with respect to which such member has a separate ownership interest or a right to exclusive possession or use.
https://www.govinfo.gov/content/pkg/USCODE-2011-title4/html/USCODE-2011-title4-chap1-sec5.htm
If the shoe fits…