Joinder

Definitions:

A joining. Joinder in action, joinder in demurrer, joinder in issue, & c., when both parties in a suit have joined issue, and have agreed to rest the decision of the cause upon the truth of the fact in question.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)

Usage examples:

11. The statute of this year provided that the husband's interest in the wife's lands should not be subject to sale by the husband without her full and free consent and joinder in the conveyance.
- School History of North Carolina by John W. Moore
This joinder of alleged offenses, one within and the other exterior to Mexico, induced me to order a special investigation of the case, pending which Mr. Cutting was released.
- Complete State of the Union Addresses from 1790 to the Present by Various