Given circuit precedent holding that tackling a fully compliant suspect by the legs was a violation of the Fourth Amendment's prohibition of unreasonable force during arrest, police should have been aware that tackling a fully compliant suspect by the arms would similarly offend; denial of qualified immunity upheld.
http://media.ca8.uscourts.gov/opndir/18/07/172633P.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.