There's this notion from the Supreme Court case *Burdick v. United States (1915) that accepting a pardon is an implicit admission of guilt. Therefore, a person can refuse a pardon. There isn't anything in the decision to justify the argument that accepting the pardon is an admission of guilt, it's just stated as a fact. It seems at odds with situations where pardons have been used to correct miscarriages of justice in cases of factual innocence.
Just to clarify, a pardon in the ordinary sense can't be refused. If you're imprisoned and the President pardon's you, you can't decide to refuse the pardon and remain in prison. As soon as the pardon is granted you are released, whether you like it or not, whether you "accept" it or not.
The Burdick case had to do with an individual who had not yet been convicted of anything being offered a pardon in exchange for testimony that could have otherwise incriminated him. The Supreme Court ruled that in that specific scenario someone accepting a pardon could be seen as admitting guilt, so the pardon couldn't be forced on Burdick to strip away his fifth amendment right and compel his testimony.
From what I recall last time I looked into it, sort of by current legal theory.
A pardon does not automatically require a confession (though it could be part of the terms), however blanket pardons remove the ability to plead the 5th on the topic if subpoenaed as a witness. The 5th precludes being forced to testify against yourself, but if the government has declared it not a crime then you can’t testify against yourself even if you wanted to.
From what I recall, non-global pardons still maintained some level of 5th Amendment protections. Ie you were pardoned for A, but talking about A might reveal you did B, so you could still potentially testify against yourself.
Iirc, non-global pardons usually come with a stipulation like “must testify that or about…” because of this.
No. Furthermore, they don't even need to name a specific crime, a person can be pardoned for "any crimes committed in this period" etc.
No; there have been a number of (controversial) pardons for people who were either not charged or had not been convicted. Gerald Ford set something of a precedent by pardoning Richard Nixon for activities related to the Watergate cover-up, and Joe Biden pre-emptively pardoned his whole family.
These applications of the pardon power have been controversial, but never successfully challenged.