You don't have an option to accept or reject a pardon, Arpaio didn't ask for it, Trump just issued it. Personally, as I said at the time, I think Trump was a little hasty, he should have waited on the appeals.
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The USSC twice rules that a person has that option. That a pardon isn't something that automatically applies, but is a document you can take to the court to use as a get out of jail free card. If a person doesn't execute the pardon, it's just a piece of paper.
When Arfpaio tried to execute the pardon to both stop the sanctions, and clear his conviction, they said the pardon doesn't erase the record. "Scooter" Libby paid $259,000 in fines and did 400 hours of community service for his conviction when Bush commuted his 30 month sentence. The Trump pardon of Libby doesn't entitle him to get the $250,000 back, or undo his community service. Those parts of his record clearly remain despite a pardon.