No abuse of discretion in denial of injunction against voting-by-mail scheme, as there is no burden placed on the voters, and, under current precedent, a claim of vote dilution would have to allege a discriminatory allocation of votes, not the de minimis individual burden here.
http://cdn.ca9.uscourts.gov/datastore/opinions/2018/06/22/18-15775.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.