Simplify the following text for a Grade 10 native English-speaking person.
Original: Pro-slavery Border Ruffians , mostly from Missouri , illegally voted in a government that Pierce recognized , and Pierce called the Topeka Constitution , a shadow government set up by Free-Staters , an act of `` rebellion . ''
Simplified: Pro-slavery Border Ruffians , mostly from Missouri , illegally voted in a government . Pierce recognized this and called the Topeka Constitution , set up by Free-Staters , as an act of â rebellion .