Black's Law Dctionary, 11th ed.
amnesty. n. [16c] 1. A pardon extended by the government to a group or class of persons, usu. for a political offense; the act of a sovereign power officially forgiving certain classes of persons who are subject to trial but have not yet been convicted undocumented aliens already present in the country> • Unlike an ordinary pardon amnesty is usu. addressed to crimes against state sovereignty — that is to political offenses with respect tol which forgiveness is deemed more expedient for the public welfare than prosecution and punishment. Amnesty is usu. general, addressed to classes or even communities. — Also termed general pardon.
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An electronic search indicates the word undocumented does not appear in the Act of 1986. In 1986, undocumented had not yet entered the realm of verbal polution.
https://www.congress.gov/99/statute/STATUTE-100/STATUTE-100-Pg3445.pdf
"Immigration Reform and Control Act of 1986".
The Act contains some relevant titles.
TITLE I—CONTROL OF ILLEGAL IMMIGRATION"SEC. 274A. (a) MAKING EMPLOYMENT OF UNAUTHORIZED ALIENS UNLAWFUL.—
TITLE V—STATE ASSISTANCE FOR INCARCERATION COSTS OF ILLEGAL ALIENS AND CERTAIN CUBAN NATIONALS
Sec. 501. Reimbursement of States for costs of incarcerating illegal aliens and certain Cuban nationals.
You may have buggered up your cut and paste of Black's definition. It doesn't much matter. The Congress essentially pardons with Acts, while the president does something a lot easier and often more self-serving. [;^)