Proving a Public Act consists of affixing the Official State Seal per 1 Stat. 122 1790 .
As for elections involving vote suppression, you must invalidate the 1864 election of The Lincoln.
On Nov. 7th, the day before the election, after Butler had placed his troops and made all arrangement necessary to control the ballot, he wrote to Secretary of War Stanton a letter in which he said:
"I beg leave to report that the troops have all arrived, and dispositions made which will insure quiet. I enclose copy of my order No. 1, and trust it will meet your approbation. I have done all I could to prevent secessionists [Democrats] from voting, and think it will have some effect."
See post #767.
As for elections involving vote suppression, you must invalidate the 1864 election of The Lincoln.
That's up to Congress to impeach and Lincoln wasn't impeached.